Hermaphroditic Duct Research Articles

The anatomy and functional morphology of the large hermaphroditic duct of three species of Aplysia, with special reference to the atrial gland.

The anatomy and functional morphology of the large hermaphroditic duct of three species of gastropod mollusc (Aplysia californica, A. dactylomela, and A. brasiliana) were examined. Each duct is composed of two parallel compartments, the red hemiduct (RHD) and the white hemiduct (WHD), which are distinguishable from the outside of the duct. Four secretory regions, all exocrine in morphology, are recognizable: the RHD secretory epithelium, the atrial gland (or atrial gland-like epithelium), the WHD secretory epithelium, and the accessory gland of the copulatory duct (AGCD). Of these regions, only the atrial gland (or atrial gland-like epithelium) contains egglaying activity and only the atrial gland (or atrial gland-like epithelium) is immunocytochemically labeled by serum antibodies generated against low molecular weight A. californica atrial gland peptides. The RHD is the functional oviduct: the egg cordon passes through a channel lined by the RHD secretory epithelium and bordered by the atrial gland (or atrial gland-like epithelium); the eggs are separated from both the WHD secretory epithelium and the AGCD by internal folds of the duct. The WHD is the functional copulatory duct: the penis, exogenous sperm, and endogenous sperm pass directly by the AGCD and in close proximity to the WHD secretory epithelium; they are separated from both the RHD secretory epithelium and the atrial gland (or atrial gland-like epithelium) by internal folds. The atrial gland (or atrial gland-like epithelium) is thus not likely to have a prostatic function or to be directly stimulated by the penis during copulation; it may play a role in oviductal function.

Sexual behavior in Aplysia fasciata induced by homogenates of the distal large hermaphroditic duct

Copulation was induced in pairs of Aplysia fasciata by adding to the environment a homogenate of the distal portion of the large hermaphroditic duct. Similar effects were not observed in response to an abdominal ganglion homogenate. The data suggest that the duct may secrete a pheromone initiating copulation in Aplysia.

COPULATION BY HYPODERMIC INJECTION IN THE NUDIBRANCHS PALIO ZOSTERAE AND P. DUBIA (GASTROPODA, OPISTHOBRANCHIA).

The Pacific nudibranch Palio (= Polycera) zosterae and the Atlantic P. dubia copulate in a manner different from that of most nudibranchs. Nudibranchs are hermaphroditic and normally copulate reciprocally, with the intromittant organ of one inserted in the vaginal opening of the other. P. zosterae and P. dubia lack a complete vaginal duct. Copulation is usually reciprocal but involves the piercing of the body wall by a barbed, eversible penial cirrus. If the cirrus injects exogenous sperm into the body wall or the haemocoel, the sperm are phagocytosed by blood cells. If the cirrus penetrates the gonad, exogenous sperm may be injected into a spermatogenic acinus. After traveling down the hermaphroditic duct to the anterior reproductive organs, these sperm presumably are sorted from endogenous sperm and stored in the receptaculum seminis. The organization of the reproductive system in Palio differs markedly from that in members of the closely related genus Polycera.

Biosynthesis of peptides in the atrial gland ofAplysia californica

1. The atrial gland of the marine molluscAplysia californica is a secretory organ in the wall of the large hermaphroditic duct of the reproductive tract. The gland contains at least three peptides capable of inducing behavioral egg laying when injected into another animal. The goals of the present study were to investigate the biosynthesis and biochemical properties of these atrial gland peptides. 2. When the atrial gland is incubated for 2 h in a medium containing a mixture of3H-amino acids, radiolabel is incorporated into a low molecular weight peptide peak (>10,000 Dalton) and a broad asymmetrical protein peak (16,000–40,000 Dalton). Egg-laying activity is recovered only from the low molecular weight peptide peak. 3. Sephadex G-50 gel filtration of radiolabelled atrial gland extracts reveals two major low molecular weight peaks: the first (peak D) is strongly labelled and has a small but variable optical density profile; the second (peak E) is weakly labelled but has a large optical density peak. Egg-laying activity is concentrated in peak D but small amounts are also present in peak E. 4. Isoelectric focusing of the material in peak D reveals three major products: a basic (pI 9.6) peak containing 31% of the incorporated label, a neutral (pI 6.6) peak containing 19% of the label and an acidic (pI 4.9) peak containing 18% of the radiolabel. A minor peak (pI 7.6) is also occasionally observed. The pI 9.6 peak, which probably contains more than one peptide, induces egg laying when injected into intact animals. 5. These experiments demonstrate that the atrial gland rapidly synthesizes both a heterogeneous group of high molecular weight proteins and a complex mixture of low molecular weight peptides. Protein biosynthesis in the atrial gland is, therefore, more complex than has previously been suggested.

Rohdella siamensis gen. et sp.nov. (Aspidogastridae: Rohdellinae subfam.nov.) from fresh water fishes in Thailand, with a reorganization of the classification of the subclass Aspidogastrea

SUMMARYRohdella siamensis, a new genus and species of aspidogastrean, is described from freshwater fishes in Thailand. A new subfamily, the Rohdellinae, is erected to accommodate this worm on the grounds that it differs from all known aspidogastreans in that the male and female ducts unite to form an hermaphroditic duct, with the result that the intromittent organ is a sinus-organ and not a cirrus. A new classification of the subclass Aspidogastrea is presented. Two orders are recognized: the Aspidogastrida, containing a single family, the Aspidogastridae, which in turn contains 3 subfamilies, the Aspidogastrinae, the Cotylaspidinae and the Rohdellinae subfam.nov.; and the Stychocotylida ord.nov., containing 3 families, the Stichocotylidae, the Multicalycidae fam.nov. and the Rugogastridae. The systematic position of the Stichocotylida, and especially the Rugogastridae, is commented upon.

Atrial gland activation of neuronal input into a buccal mass muscle of Aplysia

1. Previous studies have shown that peptides from both the bag cells and atrial gland of Aplysia cause egg-laying in Aplysia. 2. Atrial gland homogenates applied to buccal ganglia attached to buccal muscle 15 caused a longlasting, reversible increase in tonic electrophysiological activity recorded in muscle 15. Boiled atrial gland homogenates also caused the response. 3. The electrophysiological response was obtained with as little as 1 10,000 atrial gland injected into an 0.5 ml chamber and the response increased in a dose-dependent manner. 4. Specificity of the response was indicated by the lack of a similar effect with comparable tissue or protein concentrations of boiled extracts from gonad, small hermaphroditic duct, accessory genital mass, caudal large hermaphroditic duct, esophagus, crop, posterior gizzard, liver or rectum. 5. Upon fractionation on Sephadex G-50 in formic acid, atrial gland fractions most active in producing the electrophysiological response eluted with approximately the same V e V 0 as excitatory material fractionated from bag cells. 6. As little as 1 1000 atrial gland induced egg-laying in Stylocheilus longicauda. Blind injections of Sephadex G-50 fractions of atrial glands gave egg-laying only for neuroactive fractions.

An ultrastructural analysis of the mature spermatozoon of Anguispira alternata (say) (pulmonata, stylommatophora)

Mature spermatozoa from the hermaphroditic duct of adult snails were examined using various techniques of light microscopy as well as scanning and transmission electron microscopy. The sperm are approximately 557 μm in length including a dextrally spiral head approximately 13 μm long. The head consists of an electron-dense nucleus sculptured into a double-ridged spiral and an acrosome projecting approximately 0.45 μm beyond the apex of the nucleus. The acrosome consists of a membrane-bound vesicle approximately 0.1 μm in diameter and a column of homogeneous material which extends along one side of the terminal spiral of the nucleus. This material is separated from the nucleus by the nuclear envelope. The neck region, though similar to that found in other pulmonates, possesses a unique coiled structure surrounding the central doublet of the axoneme. The midpiece axoneme possesses a 9+9+2 configuration anteriorly grading into a 9+2 pattern for the majority of its length. There are three mitochondrial helices - one primary and two secondary - in the midpiece. Only the primary helix persists throughout the midpiece.

Ultrastructure of secretion in the atrial gland of a mollusc ( Aplysia)

Extracts of the atrial gland of the sea hare Aplysia californiea (Mollusca) induce egg laying when injected into mature individuals. Since egg laying is controlled endogenously by a peptide secreted by neuroendocrine cells in the central nervous system, the relationship between the atrial gland and these central neurons has become an issue of interest. With the particular objective of examining secretory structures we undertook an ultrastructural study of the atrial gland and adjacent tissues. This study revealed that the atrial gland epithelium is composed of two major cell types: ‘goblet-like’ exocrine cells containing large electron-dense granules, and ciliated ‘capping cells’. A non-secretory, and possibly post-secretory, cell containing electron-lucent granules was noted. A region of the large hermaphroditic duct contiguous to the atrial gland, known as the red hemiduct, also displayed capping cells and secretory cells with large granules. The content of these granules is organized into crista-like condensations. The cell also contains iron-rich pigment inclusions.

Evidence for an exocrine function of theAplysia atrial gland

The fact that the atrial gland ofAplysia californica contains peptides that will induce egg laying when injected into mature animals prompts consideration of the role played by the gland in the normal physiology of the animal. We have approached this consideration with a combination of morphologic and physiologic investigations. Morphologic study reveals the gland as a stratified epithelium comprised of three cell types. The only evidence for secretory activity was seen in the columnar epithelial cells containing large vesicular inclusions. These cells appear to discharge their secretory product into the lumen of the large hermaphroditic duct. While we cannot specify the contents of the secretion from the columnar cells, perfusate of the duct lumen contained bioassay active material only when the duct was exposed to depolarizing conditions. Though additional experiments in which exogenously administered atrial gland peptides were found to initiate egg laying in animals from which the source of the egg laying neurohormone had been extirpated, it appears likely that the atrial gland substances are not endocrine factors. Instead, their function must be sought among the exocrine products of the duct epithelium.

A study of gonadal organogenesis, and the factors influencing regeneration following surgical castration in Deroceras reticulatum (Pulmonata:Limacidae).

At hatching, the hermaphrodite duct of Deroceras reticulatum consists of a single cell type designated the Gonadal Stem Cell (GSC). Proliferation of the GSC leads to the formation of numerous ductules each of which forms one of the acini of the gonad. The germinal and supporting cells are derived entirely from the GSC. The germ cells differentiate first, followed by the Sertoli and follicle cells. At the early sperm stage of gonadal development the hermaphrodite duct differentiates to function as a seminal vesicle. Once the GSC are committed to this change they lose their regenerative ability. The only remaining GSC are the cells of the acinar epithelium, and these retain their germinal potential until the death of the animal. Regeneration will occur from the hermaphrodite duct provided it is in the immature state, i.e., composed of GSC, and is exposed to the hormonal conditions of a young animal. Nervous connections and the presence of an artery are not necessary for this regeneration. The presence of a functional gonad does not inhibit regeneration.

Atrial gland induction of the egg-laying response inAplysia californica

The atrial gland of the large hermaphroditic duct of the reproductive tract ofAplysia californica contains a substance that will cause egg laying when injected into sexually mature recipient animals. Preliminary chemical characterization of the atrial gland factor indicates that it is quite similar to the egg-laying hormone synthesized and secreted by the bag cell neuroendocrine organs of the central nervous system. In view of the apparent identity of its effects with those of the egg-laying hormone on presumed neural and reproductive system targets, it is possible that the atrial gland factor plays an hitherto unsuspected role in reproductive regulation. Moreover, the molecular similarity between the atrial gland factor and the egg-laying hormone suggests the possibility that the same humorally active species may be elaborated by two distinct tissue types.

The functional significance of the spermatophore and the fate of spermatozoa in the genital tract of Helix pomatia (Gastropoda: Stylommatophora)

In the Helicidae and in some other Stylommatophora the sperm are transferred in a spermatophore, even though there appears to be no need for protection of the sperm during the transfer. The function of the spermatophore and related problems concerning the genital organs of Helix pomatia were studied by means of morphological and experimental methods.The spermatophore is necessary to ensure the functioning of the female system at copulation. Its structure allows some of the spermatozoa it contains to escape through its tail canal, pass from the stalk of the bursa and reach the spermatheca by way of the oviduct; but most of the sperm pass into the bursa copulatrix and are destroyed, as is also the fate of the spermatophore. Only foreign sperm are stored in the spermatheca.Spermiogenesis was found to take place throughout the whole summer. At intervals some sperm are released from the hermaphrodite duct and are conducted via the spermoviduct and oviduct to the bursa, where they are digested. The two grooves of the spermoviduct are functionally separated only for a few minutes at actual copulation, when sperm are conducted to the copulatory organs, where the spermatophore is being formed.

The ultrastructure and activity of sperm in Acanthodoris pilosa, a nudibranchiate mollusk

The sperm of Acanthodoris pilosa were examined in fresh preparations, histochemically stained samples, electronmicroscope sections, and in paraffin sections of the whole reproductive mass. Sperm are morphologically the same in the ampulla (vas deferens) and the spermatotheca and spermatocyst (bursae for sperm received during copulation). The electron micrographs show sperm with a long spiralled, fibrous, nuclear head with non-fibrous tongue-like acrosome. The tail, attached directly to the posterior of the head, has a 9+2 filamentous arrangement surrounded by a spiralled sheath which contains mitochondria and granular thread running the length of the tail. The thin-walled ampulla contains non-motile sperm and no energy sources such as polysaccharides and lipids. The bursae hold motile sperm and, with histochemical stains, were shown to contain polysaccharide droplets in walls and lumen. The lack of self-fertilization in nudibranchs appears to be associated with a physiological immaturity of the sperm in the hermaphroditic duct, where egg and sperm meet as they leave the ovotestis.

The in Vitro Culture of Reproductive Organs of the Slug Agriolimax Reticulatus (Müll)

1. A new organ culture technique is described which has been developed for use with the slug Agriolimax reticulatus. 2. The culture medium used is capable of maintaining cells in a 'normal' state, when studied with the electron microscope, for more than 28 days. 3. Explants of hermaphrodite gland, common duct and brain were cultured in isolation and grouped in various combinations. 4. These experiments have shown evidence of hormones affecting the male cell line in the hermaphrodite gland, and secretory cells in the prostate. Key words: organ culture, hermaphrodite gland, common duct, hormone, Agriolimax reticulatus.

Histological and Histochemical Observations On the Reproductive Tract of the Hermaphrodite Pond Snail Lymnaea Stagnalis (L.)

The reproductive tract and the egg mass of Lymnaea stagnalis have been studied histologically and histochemically. The hermaphroditic duct is built up of neutral staining ciliated cells. In its distal portion the duct has large diverticula, the vesiculae seminales, which consist of large foamy cells. These cells ingest and destroy sperm. A groove with highly ciliated cuboidal or cylindrical cells is present along the length of the hermaphroditic duct. This groove is maintained throughout the greater part of the female tract, but in the male part was only observed in the prostate gland. The secretory cells of the albumen gland produce galactogen and proteins. In the rest of the female part 11 different secretory cell types could be distinguished. These cells produce different types of acid mucopolysaccharides or neutral polysaccharides. The histological findings account for 8 divisions of the female tract: 1. the albumen gland; 2. the posterior and anterior pars contorta; 3. the muciparous gland; 4. the pars recta; 5. the oothecal gland; 6. the uterus; 7. the vagina; 8. the bursa copulatrix. The histochemistry of the different parts of the egg mass is compared to that of the female tract and in this way an attempt is made to elucidate the function of the various parts of this tract. In the male part (sperm duct, prostate gland and penial complex) 13 secretory cell types were distinguished, viz., 3 in the sperm duct, 5 in the prostate gland and 5 in the praeputium. The sperm duct and the prostate gland produce mainly phospholipoproteins with some components consisting of polysaccharides and neutral fats. The function of these secretion products is assumed to be nutrition of the sperm. The secretory cells of the praeputium produce acid mucopolysaccharides, which probably play a role during copulation.

Two New Species of Dinosoma Manter, 1934 (Trematoda: Hemiuridae) from Deep-Water Macrourid Fishes off the Coast of Oregon

Dinosoma oregonensis and D. pectoralis are described from the stomachs of Chalinura pectoralis, Hemimacrurus acrolepis, and unidentified macrourids from depths of 1,000 to 2,086 m. Both species are smaller than previously described forms, have less well-developed body scales, and have a muscular extension on the dorsal lip of the oral sucker. Dinosoma oregonensis differs from D. pectoralis in possessing an inflated, subspherical posterior portion of the seminal vesicle, a more lateral genital pore and a more strongly developed muscular extension on the dorsal lip of the oral sucker. Trematodes in the genus Dinosoma Manter, 1934 have never been reported from the Pacific coast of America although they are known from the Gulf of Mexico and from Japanese waters. This paper reports two new species from deep-water macrourid fishes taken off the coast of Oregon. Manter (1934) erected Dinosoma for D. rubrum from Tortugas, Florida. Yamaguti (1938) transferred Sterrhurus robustus Manter, 1934 to Dinosoma and described D. torturm, D. synaphobranchi, D. hynnodi, D. manteri, and D. apogonis. For S. robustus, Manter (1947) later erected the genus Adinosoma which Yamaguti (1958) did not regard as valid. However, Skrjabin and Guschanskaya (1955) accepted Adinosoma and transferred three species to it: Lecithochirium exodicum McFarlane, 1936; L. japonicum Yamaguti, 1938; and L. microstoma Chandler, 1955. McCauley (1960) rejected allocation of L. exodicum to Adinosoma, and Manter and Pritchard (1960) placed it in Separogermiductus Skrjabin and Guschanskaya, 1955. MATERIALS AND METHODS Fish collected from the sea floor with an otter trawl were dead on reaching the surface. The digestive tract was injected with AFA as described by Eagle and McCauley (1965) and stained with either Van Cleave's (1923) hematoxylin combination or Mayer's carmalum, and mounted in Canada balsam. Measurements are in microns unless otherwise noted, and those for the holotype are followed by size range in parentheses. Length precedes width where two measurements are given. The sucker ratio is oral-sucker width to acetabular width norReceived for publication 16 April 1968. malized to the oral sucker. Body length does not include the ecsoma. Entire worms were drawn with a camera lucida, whereas detailed figures of the terminal genitalia are freehand and semidiagrammatic. Dinosoma oregonensis sp. n. (Figs. 1-4) Hosts: Chalinura pectoralis (Gilbert, 1891) (1 of 5); Hemimacrurus acrolepis (Bean, 1884) (4 of 19); unidentified macrourid (1 of 57). Habitat: Stomach. Location: Pacific Ocean 88 to 90 km off Oregon in depths of 1,000 to 2,086 m. Holotype: USNM Helm. Coll. No. 71290. Diagnosis (based on 87 mature specimens, 10 measured): Dinosoma. Body elongate, flattened, 1.91 (1.23 to 1.91) mm long by 0.78 (0.65 to 0.80) mm wide, ends broadly rounded, ecsoma completely retracted or only slightly extended, retracted in holotype, extended 0.39 mm in one paratype. Cuticle with weakly developed minute scales anteriorly. Oral sucker subspherical 160 (133 to 160) by 178 (163 to 195), directed anteroventrally with strong muscular extension overhanging mouth (Figs. 3, 4). Preoral lobes simple, without papillae. Acetabulum 360 (300 to 360) by 360 (295 to 375), in second fifth of body, subspherical, anteroventrally directed. Sucker ratio 1:2.03 (1.72 to 2.06). Pharynx subspherical, 87 (75 to 107) by 102 (88 to 112), posterodorsal to oral sucker; prepharynx absent. Esophagus very short, with posterior bulb from which ceca extend laterally and abruptly turn posteriorly to terminate without entering ecsoma. Genital pore ventral at midlevel of oral sucker, to left of midline; sometimes covered by preoral lobe in strongly contracted specimens (Fig. 4). Hermaphroditic duct sinuous, tubular. Testes symmetrical, immediately postacetabular, ovoid or subtriangular, smaller end medial. Right testis 120 (75 to 120) by 200 (150 to 225); left testis 173 (82 to 173) by 200 (170 to 200). Seminal vesicle bipartite; anterior portion tubular, sinuous, to right of midline; dorsal to acetabulum; posterior portion inflated, subspherical, postero-

Hemiurid Trematodes of Formosan Marine Fishes. I. Subfamilies Dinurinae and Stomachicolinae

Several species of hemiurid trematodes belonging to two subfamilies, Dinurinae Looss, 1907, and Stomachicolinae Yamaguti, 1958, are represented in a collection of helminths of Formosan vertebrates. Erilepturus formosae sp. n. (from Alectis indica) and Lecithocladium bulbolabrum sp. n. (from Rastralliger kanagurta) are described and discussed. Stomachicola muraenesocis Yamaguti, 1934, is reported again from the type host, Muraenesox cinereus. Keys to the species of Erilepturus and Lecithocladium are included. The present paper is based upon a study of trematodes collected by the third author from marine fishes while a member of the Parasitology Department of Naval Medical Research Unit No. 2, Taipei, Taiwan. This paper is part of an extensive project concerned with a study of host-parasite and zoogeographic relationships of helminths of vertebrates taken on Taiwan (Formosa) and its offshore islands. Since Looss' (1907) extensive analysis of the family Hemiuridae Liihe, 1901, a large number of subgroups have been added to it. The high degree of diversity exhibited by these various groups has resulted in state of taxonomic confusion. Yamaguti (1958), for example, recognized no fewer than 19 subfamilies containing 58 genera. Many of these subfamilies are monogeneric, monotypic, or both, and may be unwarranted. Presently, however, the family seems distinct in two major respects: (1) the vitelline follicles are compacted into masses which may be unlobed, Received for publication 14 May 1965. * This study, Project Number MR.005.09.01031.02, Bureau of Medicine and Surgery, Navy Department, was supported in part by funding under Public Law 480, Section 104(c), and in part by Public Health Service Research Grant AI-05123, from the NIAID. The opinions and assertions contained herein are those of the authors and are not to be construed as official or reflecting the views of the Navy Department or the Naval Service at large. t From a dissertation submitted in partial fulfillment of the requirements for the Master of Arts degree. t Present address: Microbiology Department, Southwest Research Foundation, San Antonio, Texas. lobed to varying degrees, or tubular, and (2) the uterus joins the male duct proximal to the genital pore, forming an hermaphroditic duct. A cirrus and cirrus pouch are absent. Characters which are too variable to be useful as family criteria are: (1) cuticular plications, (2) ecsoma (tail appendage), (3) sinus sac, (4) degree of lobation of the vitellaria, and (5) the nature of the terminal genitalia. These characters, however, are used extensively by various authors in distinguishing subfamilies and genera. The subfamily Dinurinae Looss, 1907, is one of the larger taxa of the family, characterized primarily by a long, tubular, sometimes sinuous, pars prostatica. Other genera which do not fully fit within Looss' (1907) original diagnosis (i.e., plicated cuticle, oral sucker with a large, characteristic lip, and vitellaria consisting of long, filiform tubules) have been variously added to or removed from the subfamily. Three species of hosts examined in this study (Alectis indica, Rastralliger kanagurta, and Muraenesox cinereus) were each found to be infected with a different species of hemiurid parasite. Two of these helminth species belong to the genera Erilepturus and Lecithocladium (subfamily Dinurinae) and are described below as new. The third is reported as a previously described representative of Stomachicola (subfamily Stomachicolinae Yamaguti, 1958). Keys to the species of Erilepturus and Lecithocladium are presented. MATERIALS AND METHODS Standard techniques were used to remove the trematodes from the host. The parasites were killed by quick immersion in hot water and were then transferred to stender dishes with FAA for fixation.

A morphological and histochemical study of the reproductive system of the slug, Philomycus carolinianus (Bosc)

AbstractGlycogen, determined by Best's carmine and/or PAS Tripas staining, and alkaline phosphatase, determined by the Gomori technic, occur together throughout the epithelium of the genital tract. Sites of high alkaline‐phosphatase activity are the acinar epithelium, nurse cells, and follicular cells of the ovotestis. Sperm heads are also strongly positive for the enzyme. The nidamental gland cells and the subepithelial mucous cells associated with the loop of the hermaphroditic duct and with the spermatic groove are thionine metachromatic, alcianophilic, PAS‐positive and amylase‐fast. The mucous cells of the genital atrium are PAS‐positive and amylase‐fast but lack both thionine metachromasia and affinity for Alcian blue.

POSTEMBRYONIC CHANGES IN THE REPRODUCTIVE SYSTEM OF THE SLUG ARION AFTER RUFUS L.

The morphology, histology and histochemistry of the reproductive system of Arion ater rufus (Gastropoda, Pulmonata) have been described. Contrary to previous opinion, the loop of the hermaphrodite duct has been found not to be a vesicula seminalis. Instead, the distal convoluted part of the duct acts as a true seminal vesicle. The changes which occur in the reproductive system during the life of the animal, have been examined in detail. Increasing age has a marked effect upon the development of the reproductive organs. It has been found that any of the epithelial cells of the acinar wall of ductules in the hermaphrodite gland may transform into a follicular cell. The nutritive function of nurse cells with relation to the development of spermatozoa is discussed. Fluctuations in the number of oocytes in the hermaphrodite gland have been determined and its significance in relation to the development of spermatozoa is discussed. Arion ater rufus is protandric. During the first month of life, each individual is male; from two months onwards it is a true hermaphrodite, till finally it becomes female at the age between five to twelve months. Histological observations suggest that sex determination in the gametes is the result of an inherent capacity of the acinar epithelial cells to respond in different ways to an inducing mechanism. The distribution within the reproductive system of alkaline phosphatase, lipids, glycogen and other polysaccharides has been described. The significance of the distribution and quantitative changes of these materials is discussed.

The Structure and Mode of Functioning of the Reproductive Organs of Tritonia hombergi (Gastropoda Opisthobranchia)

ABSTRACT Routine observations on Tritonia hombergi Cuvier dredged from an area off the south coast of the Isle of Man indicate that the species has an annual life-cycle similar to that of many dorid nudibranchs. The ovotestis communicates with the anterior genital mass through numbers of collecting tubules which unite to form a stout hermaphrodite duct. This duct functions as a vesicula seminalis in adult specimens; spermatozoa stored here are physiologically immature. The hermaphrodite duct bifurcates to form male and female ducts; the region of the bifurcation forms a valve ensuring that oocytes shall not enter the purely male regions of the genital system during oviposition. The male duct is the glandular and muscular vas deferens which connects with the base of the protrusible penis. The oviduct opens into the lumen of the mucus-gland. A region of convoluted tubules close to the point of the opening of the oviduct into the mucus-gland is the albumen-gland. The bursa copulatrix is a blind tubular invagination of the lateral body-wall which in mature specimens stores spermatozoa received at copulation. There are thus three external genital openings. Copulation is almost invariably reciprocal, the penis of each individual being inserted into the bursa copulatrix of the other. Secretions from the glandular linings of the bursa and of the vas deferens render spermatozoa exchanged at copulation physiologically mature; they are active and capable of fertilizing oocytes. At oviposition oocytes are expelled from the ovotestis and transported by cilia to the main hermaphrodite duct. They then travel (through the dense masses of spermatozoa in this duct) along a narrow longitudinal ciliated tract of lining epithelium; this phenomenon was clearly observed in vivisected individuals. At the hermaphrodite valve the oocytes are deflected into the oviduct and are carried by cilia into the mucusgland. In the lumen of this organ they meet active ‘foreign’ spermatozoa which have made their way from the bursa copulatrix. The oocytes and spermatozoa are now conducted along a tortuous predetermined ciliary path through the albumen-gland (where the primary egg-cases are secreted and where fertilization occurs), and then through the peripheral tubules of the mucus-gland (where successive mucous coats are added). The completed egg-string is expelled through the external female aperture and forms a ribbon which is attached to the substratum by pressure of the parent’s foot upon it. Active spermatozoa may be observed moving within the primary egg-cases for some days after oviposition.