Ontogenetic Hypothesis Research Articles

Ontogenetic correlates, not direct adaptation, explain the evolution of stelar morphology.

The primary vascular system of plants (the stele) has attracted interest from paleobotanists, developmental biologists, systematists, and physiologists for nearly two centuries. Ferns, with their diverse stelar morphology, deep evolutionary history, and prominent fossil record, have been a major focus in studies of the stele. To explain the diversity of stelar morphology, past adaptive hypotheses have invoked biomechanics, hydraulics, and drought tolerance as key selection pressures in the evolution of stelar complexity; but, these hypotheses often isolate the stele from a whole-plant developmental context, ignoring potential covariation between vascular patterning and shoot morphology. Furthermore, incongruence between expected patterns and observed data challenge adaptive hypotheses, precluding a comprehensive explanation of stelar evolution. While ontogeny has been previously recognized as a factor in stelar diversification, it has not been fully integrated into a comprehensive framework. Here we synthesize 150-years of research on stelar morphology, incorporating developmental, physiological, and phylogenetic data to present the ontogenetic hypothesis of stelar evolution. This hypothesis posits that stelar morphology is an integrated feature of whole-plant ontogeny, not a trait shaped by direct selection for adaptive patterns. This shift in perspective provides an updated framework for understanding the determinants of stelar morphology and focusses future efforts to ask more incisive questions about the evolution and function of primary vascular architecture.

Howard P. Roffwarg: sleep pioneer, legend, and ontogenetic hypothesis author.

Narrated in this article are accounts of the many contributions Howard P. Roffwarg, MD, made to the field of sleep research and sleep medicine across his entire professional career as a student, a mentor, a leader in the Sleep Research Society, a sleep medicine clinician, and a scientist who performed experimental investigations in humans and animals. Dr Roffwarg was the originator of what is known as the "Ontogenetic Hypothesis" of sleep. His research over many years on physiology has contributed greatly to much of the experimental support substantiating a role for rapid eye-movement sleep (REMS) in the early development of the brain. Though much is still unknown, the Ontogenetic Hypothesis, still to this day, inspires many neuroscientists in their investigations. These studies have demonstrated roles for both REMS and NREMS in development as well as on brain function throughout his life span. Dr Howard P. Roffwarg, is one of the legends in the field of sleep research.

New findings of the coelacanth Mawsonia Woodward (Actinistia, Latimerioidei) from the Late Jurassic – Early Cretaceous of Uruguay: Novel anatomical and taxonomic considerations and an emended diagnosis for the genus

New findings of Mawsonia from the Juro-Cretaceous Tacuarembó Formation (Uruguay) are presented. The new materials have taphonomic and anatomic significance, considering the biofabric and state of preservation of most of the bones. The most complete specimen studied is represented by several cranial and postcranial remains found in spatial association, including skull roof, cheek bones and opercula, neurocranium, palate, lower jaw, branchial and hyoid apparatuses; and also part of the shoulder and pelvic girdles. The present record is also complemented through the finding of several isolated bones from other individuals. General morphology of the bones, postparietal shield configuration and external ornamentation of dermic bones, allow to refer all the specimens to the species Mawsonia gigas. It is considered that the most complete specimen studied in this work constitutes one of the anatomically most informative records referable to this species, and to the genus, considering the following arguments: The presence of complete bones scarcely represented in previous records due to its delicate configuration, and the fact that all the remains are three-dimensionally preserved (being completely released from their sedimentary matrix). The new information provided by the comparative analyses is used for the following purposes: Bring a critical anatomical description, complement the diagnosis of the genus, and discuss previous taxonomic and ontogenetic hypotheses. The comparative analyses support previous taxonomic proposals, regarding the existence of morphological, size and ornamental variabilities, which as a whole characterize M. gigas and place it as the only recognizable species referable to this genus in South America.

«All the principles of being and becoming»: Schelling’s ontogenetic hypothesis

Schelling’s Naturphilosophie was, from the outset, more concerned with ontogeny than ontology, i.e. not on what nature is but on what it does: ubiquitous creation. Therefore, the processes articulated in the Philosophy of Mythology remain instances of a philosophy driven by what might be called a post-naturalist naturalism. The two aims of this paper are, firstly, to demonstrate this nature-philosophical continuity throughout Schelling’s so-called Protean philosophical projects in order, secondly, to re-prepare Schellingian themes for current debates concerning ontology. To this end, I draw on the worldmaking and abundance postulates of Goodman and Feyerabend, respectively, to demonstrate the persistence of Schellingian ontogenetic pathways for remodelling process metaphysics for contemporary philosophy. Finally, the paper argues that the logical form of the hypothesis (antecedent and consequent) is itself consequent upon the ontogeny it hypothesises.

Behavior of "Intermediate" Males of the Dimorphic Squid Doryteuthis pleii Supports an Ontogenetic Expression of Alternative Phenotypes.

The expression of alternative reproductive tactics (ARTs) by different-sized males of loliginid squids has been extensively investigated. In loliginids, alternative phenotypes are characterized by discontinuous differences in behavior, body size, sperm deposition site, and morphology and functioning of ejaculates. Large consort males guard females, display agonistic behaviors toward rival consort males, and mate with females in the male-parallel (MP) position. Small sneaker males avoid fighting contests and instead adopt furtive behaviors to access females guarded by consort males, mating with females in the head-to-head (HH) posture. Recently, the reappraisal of preserved material from the loliginid squid Doryteuthis pleii showed that intermediate-sized males (so-called “intermediate” males) had both sneaker- and consort-like ejaculates, leading to the hypothesis of them being a transitional stage between both phenotypes. Here, we describe observations made in captivity showing that intermediate males can display agonistic behaviors toward consort males and mate with females in both mating positions, depending on the male’s current reproductive context, i.e., generally in HH, but switching to MP when the female is laying eggs. Such unusual findings of intermediate males simultaneously displaying behaviors of both sneaker and consort males comprise additional evidence corroborating the ontogenetic hypothesis for phenotypic expression of ARTs in this species. Taken together, our results indicate that (1) instead of competing with large consort males for female access and monopolization, small/young males adopt sneaker tactics to obtain mating opportunities, and (2) as they continue to grow, they gradually modify the morphology of their ejaculates and their mating behavior, going through an “intermediate” stage, before becoming large consort males.

Lobule shape evolution inRadula(Jungermanniopsida): one rate fits all?

The quantification of lobule shape for Radula spp. shows that there is overlap in lobule shape space occupied by subgenera, such that lobule shape does not always reflect relationships. Morphological convergence caused by lineages repeatedly traversing shared regions of morphospace appears commonplace in Radula, and means that many pairs of relatively unrelated species have similar lobule shapes. When observed over time, as in comparisons between fossil and extant species, this may give the impression of stasis if fossil species resemble modern species by chance, independent of their relatedness. This poses a challenge to relating fossils of known age to extant lineages, particularly when fossils are sterile. Significant rate variation between lineages was identified by Adams' Q-mode analysis, with the fastest subgenus evolving 23 times more quickly than the slowest. Species of subgenus Volutoradula and subgenus Metaradula are apparently over-dispersed throughout lobule morphospace according to Sidlauskas' method; morphometric branch lengths and hypervolumes in other subgenera can be explained by a stochastic process. In contrast, Bayesian analysis of macroevolutionary mixtures (BAMM) identified a single evolutionary rate as having the highest posterior probability. Consideration of the three independent accessions into auriculate lobule morphospace by Cladoradula and Radula, wherein convergent lobule shapes result from convergent lobule ontogenies and are correlated with bipinnately branched shoot systems and robust primary stems, leads to an ontogenetic hypothesis driven by structural requirements for light interception, under which auriculate lobules are a spandrel. It is speculated that lobules themselves, however, may be a key innovation facilitating radiation into microsites devoid of or depauperate in fungal endophytes.

The limits of understanding in biological systematics

Ernst Mayr’s (1961, Science 131: 1501–1506) distinction between proximate and ultimate causation in biology is examined with regard to the acquisition of understanding in biological systematics. Rather than a two-part distinction, understanding in systematics is characterized by relations between three explanatory components: descriptive (observation statements)—proximate (ontogenetic hypotheses)—ultimate (e.g. specific and phylogenetic hypotheses). Initial inferential actions in each component involve reasoning to explanatory hypotheses via abductive inference, providing preliminary understanding. Testing hypotheses, to critically assess understanding, is varied. Descriptive- and proximate-level hypotheses are routinely tested, but ultimate hypotheses present inherent difficulties that impose severe limits, contrary to what is usually claimed in the systematics literature. The problem is compounded by imprecise considerations of ‘evidence’ and ‘support.’ For instance, in most cases, the ‘evidence’ offering ‘support’ for phylogenetic hypotheses, as cladograms, is nothing more than the abductive evidence (premises) used to infer those hypotheses, i.e. character data and associated phylogenetic-based theories. By definition, such evidence only offers initial, trivial understanding, whereas the pertinent evidence sought in the sciences is test evidence, which cannot be supplanted by character data. The pursuit of ultimate understanding by way of spurious procedures such as contrived testing, Bremer support, and resampling methods are discussed with regard to phylogenetic hypotheses.

The world’s smallest vertebrate species of the genus Paedocypris: A new family of freshwater fishes and the sister group to the world’s most diverse clade of freshwater fishes (Teleostei: Cypriniformes)

The genus Paedocypris has only recently been discovered and described and includes three species, all of which are miniature species and one, P. progenetica, is the smallest vertebrate species. Two previous studies investigating relationships of Paedocypris, based on either cytochrome b or morphology, placed the genus with Sundadanio and Danionella, two genera with miniature species in the formerly recognized family Cyprinidae. Our investigation of the phylogenetic relationships of Paedocypris using six nuclear genes and a broad survey of taxa in major lineages of the Cypriniformes identifies Paedocypris as a monophyletic group and the basal sister group to all Cypriniformes, not a species of the formerly recognized family Cyprinidae. These new relationships are also supported by previously proposed morphological characters but reinterpreted relative to ontogenetic hypotheses and outgroup comparisons used to determine synapomorphies. Miniaturization has occurred independently multiple times in the order, but mostly in the Rasborine Clade. Consequently, the hypothesis of a shared ancestral developmental truncation of multiple morphological features in genera with miniature species is rejected. While strong evidence exists for the new phylogenetic placement of Paedocypris as the sister group to the most diverse clade of freshwater fishes attempts to theorize more broadly as to evolutionary processes of miniaturization would be premature without more complete taxon sampling.Accompanying growing consistency of phylogenetic evidence of relationships in the Cypriniformes has come the consistent support of major clades within the previously recognized family Cyprinidae now recognized as a series of separate families, rendering the former Cyprinidae equivalent to Cyprinoidea. The revised family Cyprinidae includes species of the former subfamily Cyprininae, sister to Psilorhynchidae. The former subfamilies of Cyprininae, Acheilognathinae, Leuciscinae, and Gobioninae are elevated to families, and in keeping with consistency between phylogenetic relationships and classification the families Leptobarbidae and Tincidae are now recognized and the new families Tanichthyidae and Sundadanionidae are described. Paedocypris is recognized in a new superfamily, Paedocypridoidea, and family, Paedocyprididae.

Rapid Eye Movement Sleep and General Anesthesia

University of Michigan Medical School, Ann Arbor, Michigan. gmashour@umich.edu(Mashour)I read with great interest the article by Leslie et al .1describing the electroencephalographic correlates of dreaming during anesthesia. Their conclusion that traits of rapid eye movement (REM) sleep are expressed during emergence from anesthesia is provocative. It is of historical interest to note that a common mechanism of dreaming during both sleep and anesthesia was predicted by the psychoanalyst Paul Federn, after the self-analysis of a dream that he experienced under nitrous oxide. Federn discussed this in a 1943 lecture to the American Psychoanalytic Association—one decade before the discovery of REM sleep by Aserinsky and Kleitman2—and, in a later publication, concluded that “one can expect to find the basic mechanisms in dream-production during general anesthesia will not differ from those in dream-production during physiologic sleep.”3More modern concepts of relevance to the work by Leslie et al . include “covert REM” and REM sleep as a form of “protoconsciousness.” Nielsen4suggested that isolated REM sleep traits could be expressed during non-REM sleep, thereby accounting for dreaming and mentation during this stage. Therefore, the covert REM hypothesis is consistent with the “simple” anesthesia-related dreams that Leslie et al . describe, which are more characteristic of non-REM dreams despite the electroencephalographic REM-like traits. The framework of covert REM during emergence from anesthesia fits well with the observed data distinguishing the anesthetic dreamer and nondreamer and avoids the need to account for every component of classic REM sleep (e.g ., muscle atonia).Also of relevance is the suggestion that REM sleep represents a form of protoconsciousness,5a view derived, in part, from the observation that REM sleep occurs during gestation.6The “ontogenetic hypothesis” put forth by Roffwarg et al .7in 1966 suggests that the endogenous process of cortical activation associated with REM sleep prepares the fetus or developing animal for sensory experience. It is of interest to consider whether REM sleep-like traits are a similar form of protoconsciousness that may precede the planned or unplanned emergence from general anesthesia.University of Michigan Medical School, Ann Arbor, Michigan. gmashour@umich.edu

Beyond dreams: do sleep-related movements contribute to brain development?

Conventional wisdom has long held that the twitches of sleeping infants and adults are by-products of a dreaming brain. With the discovery of active (or REM) sleep in the 1950s and the recognition soon thereafter that active sleep is characterized by inhibition of motor outflow, researchers elaborated on conventional wisdom and concluded that sleep-related twitches are epiphenomena that result from incomplete blockade of dream-related cortical activity. This view persists despite the fact that twitching is unaffected in infants and adults when the cortex is disconnected from the brainstem. In 1966, Roffwarg and colleagues introduced the ontogenetic hypothesis, which addressed the preponderance of active sleep in early infancy. This hypothesis posited that the brainstem mechanisms that produce active sleep provide direct ascending stimulation to the forebrain and descending stimulation to the musculature, thereby promoting brain and neuromuscular development. However, this hypothesis and the subsequent work that tested it did not directly address the developmental significance of twitching or sensory feedback as a contributor to activity-dependent development. Here I review recent findings that have inspired an elaboration of the ontogenetic hypothesis. Specifically, in addition to direct brainstem activation of cortex during active sleep, sensory feedback arising from limb twitches produces discrete and substantial activation of somatosensory cortex and, beyond that, of hippocampus. Delineating how twitching during active sleep contributes to the establishment, refinement, and maintenance of neural circuits may aid our understanding of the early developmental events that make sensorimotor integration possible. In addition, twitches may prove to be sensitive and powerful tools for assessing somatosensory function in humans across the lifespan as well as functional recovery in individuals with injuries or conditions that affect sensorimotor function.

Interaction of foliage and larval age influences preference and performance of a geometrid caterpillar

AbstractIn two recent studies it was reported that feeding on foliage of multiple age classes can improve insect fitness, but it was not determined whether the increase in fitness was due to larvae obtaining a more balanced diet (the balanced-diet hypothesis) or to a difference in the nutritional requirements between young and old larvae (the ontogenetic hypothesis). To test these two hypotheses, we examined the foraging behaviour and performance of young (second or third to fourth instar) and old (third or fourth to fifth instar) larvae of the pale-winged gray moth, Iridopsis ephyraria (Walker) (Lepidoptera: Geometridae), on different-aged foliage of eastern hemlock, Tsuga canadensis (L.) Carrière (Pinaceae), during an outbreak in southwestern Nova Scotia. Defoliation attributed to I. ephyraria was highest on current-year foliage and gradually declined with foliage age. Young larvae were only observed feeding on current-year shoots but old larvae fed on foliage of all ages. When forced to feed on foliage of specific ages in manipulative field studies, survival rates of young and old larvae were highest on current-year and old (≥1 year old) foliage, respectively. However, both young and old larvae had higher survival rates when provided with access to foliage of all age classes than when they were forced to feed on only young or old foliage. Thus, this study supports both the balanced-diet and ontogenetic hypotheses.

Spontaneous performance of wild baboons on three novel food-access puzzles

Although the technical problem-solving expertise of nonhuman primates has been investigated extensively in captivity, few species have been tested in their natural habitats. Here I examine the physical cognition of wild savanna baboons (Papio anubis), a species that occupies an omnivorous foraging niche in which a variety of embedded food items are extracted and processed. Baboons were tested on three puzzles, each involving high-quality food that required removal from a novel obstruction: (1) a string-pulling puzzle in which food was hung from tree branches, (2) a twig-dipping puzzle in which food was embedded in a vertical tube, and (3) a stick-pushing puzzle in which food was contained in a horizontal conduit. The baboons failed to solve the second and third puzzles even when tools had been appropriately positioned in advance. And although they solved the first puzzle, their actions (running while holding food that was still attached to the string), suggested they did not fully comprehend the string's connective property. The baboons' performance might reflect the time constraints of life in the wild, which relative to captivity may provide fewer opportunities for the development of understanding about the physical properties of objects and their potential uses as tools. Further experiments on the physical cognition of baboons and many other primate species in their natural habitats would help test this ontogenetic hypothesis. Such field experiments would be especially fruitful if they continued to target extractive foragers like baboons: these experiments could simultaneously provide a test of phylogenetic hypotheses that invoke extractive foraging as the key stimulus for brain expansion in savanna-dwelling hominids.

Human cortical dysplasia and epilepsy: an ontogenetic hypothesis based on volumetric MRI and NeuN neuronal density and size measurements.

In epilepsy patients with cortical dysplasia (CD), this study determined the probable ontogenetic timing of pathogenesis based on the number, location and appearance of neurons. Magnetic resonance imaging (MRI) determined gray and white matter volumes of affected and non-affected cerebral hemispheres, and gray and white matter neuronal-nuclear protein (NeuN) densities and sizes were assessed in epilepsy surgery patients (0.2-38 years) with CD (n = 25) and non-CD etiologies (n = 14), and compared with autopsy cases (n = 13; 0-33 years). Pathology group, seizure type and age at surgery were compared against MRI and NeuN data. CD patients demonstrated increased MRI cerebral (3%) and gray matter (8%) volumes of the affected compared with non-affected cerebral hemisphere, and increased layer 1 (131%), upper cortical (9-23%) and white matter (28-77%) NeuN densities compared with autopsy cases. Non-CD cases showed decreased cerebral volumes of the affected hemisphere (14-18%) without changes in NeuN densities. Compared with autopsy cases, in CD and non-CD patients, cortical neurons were hypertrophied. Patients with a history of infantile spasms had a 40% increase in the size of layer 1 neurons compared with cases without spasms. By age, regardless of pathology group, there were logarithmic increases in MRI cerebral and white matter volumes, logarithmic increases in the size of lower gray and superficial white matter neurons, and logarithmic decreases in gray and white matter neuronal densities. These results support the concept that there were more neurons than expected in layer 1, gray, and white matter of CD patients compared with non-CD and autopsy cases. In addition, the location and appearance of neurons are consistent with the hypothesis that CD is the consequence of abnormalities occurring late in corticoneurogenesis that involve excessive neurogenesis with retention of pre-plate cells in the molecular layer and subplate regions.

Cognitive representation of negative numbers.

To understand negative numbers, must we refer to positive number representations (the phylogenetic hypothesis), or do we acquire a negative mental number line (the ontogenetic hypothesis)? In the experiment reported here, participants made lateralized button responses to indicate the larger of two digits from the range -9 to 9. Digit pairs were displayed spatially congruent or incongruent with either a phylogenetic or an ontogenetic mental number line. The pattern of decision latencies suggests that negative numbers become associated with left space, thus supporting the ontogenetic view.

Fetal development of the first metatarsophalangeal joint complex with special reference to the intersesamoidal ridge

In most individuals, plantar to the first metatarsal head, a more or less well developed crest separates the two furrows for the medial and the lateral sesamoid bones. In some instances, the absence of this crest has been observed in a previous study. This observation may be related to a pathological and/or an ontogenetic development. For the present examination, we have assumed the ontogenetic hypothesis. Twenty-two feet were examined at different developmental stages from week 12 to 38. The feet were prepared for examination using methods of plastination-histology. Sesamoids have already developed from the joint capsule by the first stage (12th week). Attachment bundles of collagenous fibers have deeply penetrated the cartilage of the sesamoids on their capsular side. Only some inner fibers of the muscular tendons join the sesamoids on their plantar side. The intersesamoid ligament is blended into the synovial tendon sheath of the flexor hallucis longus. The plantar crest has already developed in the fetal cartilage of the first metatarsal head as a strong ridge. With further growth, the surfaces become inwardly tapered on both sides of the ridge through the sesamoid bones, so that in the end the ridge results in a more or less clear crest. If the tapering of the furrows for the sesamoid bones proceeds too briskly or too far, this can result in an absence of the plantar crest. If the absence of this crest stands in relation to the formation of a Hallux valgus, this result would be a first indication of an developmentally based cause for this wide-spread disease of the foot.

Incidence and functions of self-reported private speech in young adults: A self-verbalization questionnaire.

AbstractA self-report questionnaire assessing the use of self-directed was administered 1,132 undergraduateuniversity students. In general, self-verbalization scoreswere high. Exploratory factor analysis produced a four-factor solution that was readily interpretable in terms ofVygotskian theory. Consistent with the view that privatespeech serves as a cognitive tool system, the highest scoreswere reported for questionnaire items loading highly on afactor consisting of cognitive, mnemonic, and attentionaluses of self-verbalization. The scales appear have goodinternal consistency, high test-retest reliability, and goodcontent and criterion validity.ResumeOn a demande a 1132 etudiants au niveau dubaccalaureat de remplir un questionnaire et d'auto-evaluer par le fait meme 1'usage qu'ils font de 1'auto-verbalisation. Dans 1'ensemble, les scores etaient eleves.A resulte d'une analyse factorielle exploratoire uneformule de quatre facteurs que Ton a pu interpreterfacilement d'apres la theorie de Vygotskian. Partant d upoint de vue voulant que 1'autoverbalisation serve desysteme cognitif, les scores les plus eleves sont attribuesaux questions qui insistaient beaucoup sur 1'usage de1'autoverbalisation a des fins cognitives, mnemoniques etattentionnelles. Les echelles devaluation semblentcomporter un bon indice de coherence interne, un coef-ficient de test-retest eleve, et une validite de contenu et decriteres satisfaisante.Private speech is overtly vocalized directed tothe speaker himself or herself. The extensive empiricalliterature on private in children (e.g., Berk, 1992)has been motivated by an ontogenetic hypothesis pro-posed by L.S. Vygotsky (1934/1987,1978). According tothis view, children use overt self-verbalization exten-sively between the ages of three and eight years, afterwhich it is transformed into inner or covertverbal thinking. Vygotsky (1934/1987) argued that theuse of private is limited a particular transi-tional stage (p. 71) in the development of verbal thinkingand that overt self-directed does not occur beyondthe early school years. Recent work (Duncan, 1998)supports the position that adults also use private speechfor the same purposes Vygotsky identified in youngchildren, including analysis of task situations, co-ordina-tion of actions during transitions within tasks, planningand organization, evaluation of or commentary onoutcomes of actions, and emotional discharge(Vygotsky, 1934/1987, p. 70).Private in adults has received little attentionfrom researchers. Kronk (1994) documented privatespeech by 98% of a sample of older adolescents workingon paper-and-pencil tasks. Siegrist (1995) constructed aself-report questionnaire measuring both overt andcovert self-verbalization in undergraduates, specifically,talking to oneself about oneself (p. 259). The presentreport is the first employ the self-report approach tostudy the cognitive and self-regulatory functions ofprivate speech, described by Vygotsky (1934/1987,1978),in young adults.METHODParticipantsThe sample was drawn from introductory psychologyclasses at the University of Waterloo during three consec-utive terms, N = 1,132 (509 males and 623 females), withM age = 20.06 years (SD = 3.29; range = 17 47 years).Materials and ProceduresThe Self-Verbalization Questionnaire (SVQ) is a self-reportinstrument on self-directed speech, comprising 27 itemswith 7-point Likert scales (see Appendix A). Guided byVygotsky's (1934/1987,1978) functional analysis, itemswere chosen capture a range of activities and situa-tions. Copies of the SVQ were included in bookletsdistributed students. One two months following theinitial administration, 46 participants completed the SVQ

Sleep for development or development for waking? — some speculations from a human perspective

The issue of the relationship between sleep and development could be posed in the following terms: (1) does sleep have a function for development? and (2) which is the specificity of sleep function during development? Is it possible to assess critical ages of emergence and decline of specific sleep functions? The results of recent investigations related to the so-called ontogenetic hypothesis for the function of rapid eye movement (REM) sleep will be reviewed; suggestions are put forward concerning the possible role of non-rapid eye movement (NREM) sleep. Because of the difficulties to provoke long-lasting sleep deprivation in humans during development, two different approaches were used. The results of one set of analyses concerned the secretion of growth hormone during sleep under normal and pathological conditions and the relationship between sleep organization and nutritional supply utilisation in infants and children. The second approach aimed at investigating the long-term development of children suffering from sleep abnormalities at earlier ages. Furthermore, the role of dreaming during development will be discussed. The data summarized here only partly support the function of sleep during development; we would like to underscore the difficulty to dissociate the function of sleep from that of waking.

Development, trends and phylogenetic inference

An analysis of the development and history of theearly tetrapod limb and cranium is used to examine phylogenetic inference, recapitulatory and other developmental hypotheses. The use of recapitulatory ontogenetic hypotheses in phylogenetic inference is questioned by modern aspects of embryological studies, because the developmental patterns may evolve by omitting or modifying ontogenetic stages. Fossil taxa play an important role in the reconstruction of hypothetical transformation series. Furthermore an understanding of patterns of development is important in aiding the interpretation of transformation series such as in the evolution of the tretrapod limb. There is need for more complete theories of phylogenetic relationships among and within clades, so as to determine the limits set by developmental mechanisms, biomechanics and history.

Postembryonic dimensional allometry of the human femur.

Developmental constraints can affect evolution. McMahon 's (1973, 1975a ) hypothesis of elastic similarity is tested as an epigenetic rule. This is an ontogenetic hypothesis that previously has not been tested with ontogenetic data. Cross-sectional data from the human femur are analyzed. Length-diameter relationships for phases of growth and aging are calculated with bivariate allometry. McMahon 's hypothesis cannot be rejected, although most of the calculations are not consistent with it. Ontogenetic skeletal allometry is complex because both material and geometric properties change during development.

Sleep deprivation and measures of emotionality in rats.

ABSTRACTPredictions from two theories which attempt to explain the function of active sleep (AS) were tested on 144 rats. Total sleep deprived, activity control, stationary control, active steep deprived, large pedestal control, or homecage control conditions were imposed on 30‐day and 90‐day‐old subjects for 5 days. Open‐field (OF) and startle response measures and adrenal and body weights permitted examination of changes in emotionality. Increases in OF activity and decreases in defecation in this paradigm are attributed primarily to AS deprivation, while reductions in quiet sleep may account for elevated startle responsivity in totally deprived subjects. Limited support for the Ontogenetic hypothesis is found in the treatment by age effect for OF activity, but the P‐hypothesis prediction of increased emotionality in AS deprived subjects is contradicted by our data.