Tentacular Bulbs Research Articles

A New Species of Hydrozoan Jellyfish Eutima onahamaensis and New Record of Eutima diademata (Hydrozoa, Leptothecata) from Japan

The family Eirenidae is one of the major taxa of the order Leptothecata, comprising approximately 80 species from ten genera. In this study, taxonomic investigations, including morphological observations and molecular 16S phylogenetic analyses, were conducted on unknown Eirenidae specimens collected off the coast of Iwaki, Fukushima Prefecture, eastern Japan, in June 2022. The specimens had the following morphological characteristics: marginal warts and tentacular bulbs with lateral cirri and without adaxial papillae, a mouth with simple lips, four simple radial canals, and eight statocysts common to the genus Eutima. However, this species can be distinguished from other species of Eutima by the number of tentacles, number and shape of marginal warts, position of the gonads, and gastric peduncle length. Moreover, the monophyly of the species was evident in the 16S rRNA phylogenetic tree (as indicated by the high bootstrap value of 100%), thereby supporting the validity of the new species. Based on these results, we describe it as a new species, Eutima onahamaensis, for taxonomic stabilization. We also made detailed observations of the morphology and molecular phylogenetic analyses of one of the species newly recorded in Japan: Eutima diademata. A comparative table of the primary diagnostic characteristics of Eutima has been provided. This study provided taxonomic keys for identifying species in the genus Eutima.

A new species of Grillotia Guiart, 1927 (Cestoda: Trypanorhyncha) from the spotted skate, Raja straeleni Poll, in South Africa

A new species of Grillotia Guiart, 1927 was recovered from the spotted skate (Raja straeleni Poll) from the south coast of the Western Cape, South Africa. Grillotia sasciae n. sp. is described based on morphological and molecular data. This species most closely resembles species in the subgenus Grillotia (viz., Grillotia borealis Keeney and Campbell, 2001, Grillotia brayi Beveridge and Campbell, 2007, Grillotia dollfusi Carvajal, 1971, Grillotia erinaceus Dollfus, 1969, Grillotia musculara Hart, 1936 and Grillotia patagonica Menoret and Ivanov, 2012) in having four hooks per principal row and intercalary hook rows in the metabasal region of the tentacular armature, a band of hooks on the external tentacular surface, numerous proglottids, and the presence of an uterine pore, a hermaphroditic sac, and internal and external seminal vesicles. The molecular phylogenetic analysis of the partial 28S rDNA gene, confirms the morphological data as it also groups Grillotia sasciae n. sp. within the G. erinaceus species complex. Grillotia sasciae n. sp. is distinctive among all other valid species in the complex by having two enlarged, uncinate hooks in the basal armature, of a different shape and size from the remaining hooks 1(1') in the metabasal armature. In addition, the retractor muscle of Grillotia sasciae n. sp. attaches at the posterior region of the tentacular bulb rather than the middle portion, continuing posteriorly as seen in most congeners (viz., G. erinaceus, G. borealis, G. brayi, G. musculara and G. pantagonica). The new species is the seventh species within the subgenus Grillotia and the first record of a species of Grillotia from southern African waters.

New species of Eirenidae (Hydrozoa: Leptothecata) from the Amazonian coast (northern Brazil)

Two new Eirenidae medusae species were collected on the Amazonian coast, Eutima marajoara n. sp. and Helgicirrha angelicae n. sp. The former differs from other species of the genus by the gonads extending along almost the entire length of the subumbrellar portion of the radial canals but not connected to the ring canal, up to 40 marginal tentacles with conical bulbs and 48 marginal warts, lateral cirri and adaxial papillae on some marginal warts and tentacular bulbs. Helgicirrha angelicae n. sp. differs from other species of the genus by the gonads on the middle portion of the radial canals with medusa buds, the short gastric peduncle, up to 20 marginal tentacles, some with adaxial papillae, up to three marginal warts and two statocysts between successive tentacles, and lateral cirri both on tentacle bulbs and marginal warts.

The ecology and developmental changes of meristic characters of the medusa Malagazzia carolinae (Hydrozoa: Leptothecata) from subtropical Southwestern Atlantic estuaries

In the present study we show that the meristic marginal characters of the hydromedusa Malagazzia carolinae changes through its ontogeny. We additionally present background-data on abundance and size composition spatial temporal dynamics of this poorly-known medusa from five subtropical Brazilian estuaries (∼24–26.5°S). Data presented are important to improve taxonomy of the group and to track life-history strategies. The number of marginal structures varies considerably: tentacular bulbs ranged between 0 and 7, rudimentary bulbs between 0 and 12 and statocysts between 1 and 22 on each quadrant and their numbers tended to increase with bell diameter. Malagazzia carolinae was nearly absent from the open shallow shelf, and among the five estuaries sampled it was more common and abundant inside Babitonga and Guaratuba Bays, where a well-defined distribution was found, with peaks in January mostly in the inner sectors (mean 8–10ind. 10m−3). Although sampled in wide hydrographic conditions, M. carolinae was mostly found in intermediate salinities (21–26) and temperatures (22–29°C), suggesting it is well adapted to thrive in estuarine subtropical and tropical systems.

First record of the hydromedusa Aequorea macrodactyla (Leptothecata: Aequoreidae) in Brazilian waters

Three Aequorea macrodactyla (Brandt 1835) medusae were found along the Sao Paulo and Rio de Janeiro coasts. The specimens clearly match the diagnosis of the species, as they have tentacular bulbs with a large abaxial keel and a prominent excretory pore and papilla. The number of tentacles is approximately three times smaller than the number of radial canals. In the southwestern Atlantic, this species was previously known from Patagonian waters and this is the first record from the non-temperate southwestern Atlantic. Additionally, a thorough review of meristic data is provided for this hydrozoan species.

Trypanorhynch cestodes from elasmobranchs from the Gulf of Oman, with the description of Prochristianella garshaspi n. sp. (Eutetrarhynchidae)

In a study on the order Trypanorhyncha Diesing, 1863, a total of 35 specimens belonging to nine species of elasmobranch in the Gulf of Oman, was examined. The following trypanorhynch species were identified: Pterobothrium lesteri Campbell & Beveridge, 1996, Otobothrium carcharidis (Shipley & Hornell, 1906), Eutetrarhynchus platycephali Palm, 2004, Parachristianella indonesiensis Palm, 2004, Pa. monomegacantha Kruse, 1959 and Prochristianella mooreae Beveridge, 1990. Prochristianella garshaspi n. sp. is described from Pastinachus sephen (Forsskål) and Rhinoptera sp. The new species is allocated to the genus Prochristianella Dollfus, 1946 on the basis of the presence of two bothria, prebulbar organs, and a heteroacanthous typical tentacular armature with relatively few hooks in each principal row, hollow hooks increasing in size from antibothrial and then decreasing towards the bothrial surface of the tentacle, hooks 1 and 1' being separated, and a basal swelling with characteristic billhooks increasing in size towards the bothrial surface. The lack of microscopically visible microtriches on the scolex distinguishes the new species from P. hispida (Linton, 1890), P. clarkeae Beveridge, 1990, P. thalassia (Kovaks & Schmidt, 1980), P. multidum Friggens & Duszynski, 2005 and P. cairae Schaeffner & Beveridge, 2012. Prochristianella garshaspi n. sp. can be distinguished from the remaining species within the genus by a combination of the following morphological features: the presence of numerous gland-cells within the tentacular bulbs, the number of rows on the basal swelling, the number of hooks per half spiral row, the size of the principal hooks, the number of the testes and the presence of an external seminal vesicle.

Prochristianella Dollfus, 1946 (Trypanorhyncha: Eutetrarhynchidae) from elasmobranchs off Borneo and Australia, including new records and the description of four new species

Prochristianella cairae n. sp. is described from the spiral intestines of two species of bamboo sharks, Chiloscylliumpunctatum Müller & Henle and Chiloscyllium indicum (Gmelin) (Hemiscyllidae) off the coast of Malaysian Borneo. Thespecies is distinguished from congeners by enlarged microtriches covering the whole scolex peduncle, a uniquearrangement of hooks on the basal swelling, a dissimilar number of hooks in each principle row in the metabasal armatureand hook files 1 and 1’ not being distinctly separated. Prochristianella jensenae n. sp. is described from the spiralintestines of three species of whiptail stingrays, Pastinachus solocirostris Last & Manjaji-Matsumoto, Pastinachus atrus(Macleay) and Pastinachus gracilicaudus Last & Manjaji-Matsumoto (Dasyatidae) from coastal waters off Indonesianand Malaysian Borneo and Western Australia, from Himantura uarnak (Gmelin) (Dasyatidae) off Nickol Bay, WesternAustralia and from Rhinoptera neglecta Ogilby (Myliobatidae) off Weipa, Queensland, Australia. This species lacksgland-cells within the tentacular bulbs, one of the most distinctive features of this family. Prochristianella kostadinovaen. sp. is described from the spiral intestines of Himantura uarnak 2 (Dasyatidae) (sensu Naylor et al. 2012) from the Gulfof Carpenteria. It differs from congeners in its metrical data, a metabasal tentacular armature with 10 hooks per principlerow, hooks 1(1’) being uncinate with an elongate base and widely spaced and hooks 4(4’) smaller than neighbouring hooks3(3’) and 5(5’). Prochristianella scholzi n. sp. is described from specimens of the Taeniura lymma species complex(Dasyatidae) (sensu Naylor et al. 2012) from three localities in Malaysian and Indonesian Borneo. This species has arraysof billhooks on the basal swelling, but differs from similar congeners in having very few, tiny gland-cells within thetentacular bulbs and a metabasal tentacular armature with 9–10 hooks per half spiral row and hooks 4(4’) being muchsmaller than the neighbouring hooks 3(3’) and 5(5’). Examinations of new material from northern Australia andIndonesian and Malaysian Borneo provided additional information on Prochristianella aciculata Beveridge & Justine,2010, Prochristianella butlerae Beveridge, 1990 and Prochristianella clarkeae Beveridge, 1990. In total, 17, 7 and 29(respectively) new host records and 14, 9 and 28 (respectively) new locality records are added. These records extend thegeographical range of all three species in the Australasian region and also represents the first record of P. aciculata fromAustralian waters and the first record of P. butlerae from the Indo-Malayan region. Prochristianella clarkeae is the least host specific taxon within Prochristianella, infecting 43 different host species.

Description of Plerocerci and Adults of a New Species ofGrillotia(Cestoda: Trypanorhyncha) in Teleosts and Elasmobranchs From the Patagonian Shelf Off Argentina

A new species of Grillotia was found from teleosts and elasmobranchs along the Patagonian shelf off Argentina. Grillotia patagonica n. sp. is described from plerocerci recovered from gadiform (Moridae) and perciform fish (Cheilodactylidae, Bovichtidae, and Nototheniidae) and adults from the smallthorn sand skate Psammobatis rudis (Rajiformes, Rajidae). Grillotia patagonica most closely resembles species in the Grillotia erinaceus species complex (viz., Grillotia borealis, Grillotia brayi, Grillotia dollfusi, G. erinaceus, and Grillotia musculara) in having 4 hooks per principal row and 2 or more intercalary rows in the metabasal region, a band of hooks on the external surface of the tentacle, numerous proglottids, a hermaphroditic sac, internal and external seminal vesicles, uterine pore, and attachment of the retractor muscle in the mid region of the tentacular bulb. Grillotia patagonica n. sp. is unique among all valid species in the genus by having the hooks on the first row reduced and of a different shape from the rest of the metabasal rows. Despite the diversity of elasmobranchs that are available as definitive hosts for species in Grillotia, most species (10/14) are oioxenous or mesostenoxenous. The specificity for the last intermediate host is variable among species of Grillotia, with most plerocerci being oioxenous (5/15) or euryxenous (8/15). Host specificity is higher for the adult stage in the definitive host (mean HS(S) = 4.07) than for the plerocerci (mean HS(S) = 7.30). All the species with oioxenous specificity (either larvae or adults) have limited geographic distributions. Some previous records of species of Grillotia from fishes caught off Argentina require reconsideration, i.e., G. erinaceus, Grillotia minuta (reported as Grillotia bothridiopunctata) and G. borealis . An updated host-parasite checklist for the valid species of Grillotia is also presented along with new host records for Grillotia carvajalregorum.

Ancipirhynchus afossalis n. g., n. sp. (Trypanorhyncha: Otobothriidae), from two species of sharks off Indonesian and Malaysian Borneo

A new genus of trypanorhynch cestode is described from two species of sharks, the sliteye shark Loxodon macrorhinus Müller & Henle and the straight-tooth weasel shark Paragaleus tengi (Chen) collected in the Makassar Strait (off Indonesian Borneo) and Sulu Sea (off Malaysian Borneo). Ancipirhynchus afossalis n. g., n. sp. possesses two bothria and a heteroacanthous, heteromorphous tentacular armature with three distinctive files of hooks on the external tentacle surface but lacks prebulbar organs and gland cells within the tentacular bulbs. The hook arrangement of alternating files on the external surface of the tentacle resembles that seen in the superfamily Otobothrioidea Dollfus, 1942 in the genus Fossobothrium Beveridge & Campbell, 2005. However, the new species lacks the defining characteristic of this group, i.e. the paired bothrial pits. A Bayesian inference (BI) analysis of 37 LSU sequences of trypanorhynchs from three superfamilies provided evidence supporting the taxonomic placement of Ancipirhynchus afossalis n. g., n. sp. within the Otobothrioidea.

Distribution pattern of GFP (green fluorescent protein) in a bivalve-inhabiting hydrozoan, Eutima japonica (Leptomedusae: Eirenidae)

Bright green auto-fluorescence was observed in the umbrellar margin, umbrellar marginal warts, tentacular bulbs, tentacles, and manubrium of laboratory-reared immature (1–14 days old) medusae of Eutima japonica from Japan and China. In vivo microscopic fluorescence spectra showed that the green fluorescence was similar to that of green fluorescent protein (GFP) found in Aequorea victoria, although the maximum emission wavelength (503 nm) was slightly bluer. No fluorescence was detected in the cirri, statocysts, radial canals, velum, or subumbrella of the medusae. The fluorescence distribution pattern in E. japonica more closely resembles that of Eugymnanthea inquilina from the Mediterranean Sea than that of Japanese Eugymnanthea japonica, which is the derived species of E. japonica. This suggests that the common fluorescence pattern is convergently evolved in the former two species, perhaps owing to the as yet unclarified physiological and/or ecological function of GFP and/or GFP-like proteins.

Revision of the Grillotia erinaceus (van Beneden, 1858) species complex (Cestoda: Trypanorhyncha), with the description of G. brayi n. sp.

Members of the trypanorhynch cestode genus Grillotia Guiart, 1927 belonging to the Grillotia erinaceus (van Beneden, 1858) species complex are redescribed. The type-species of the genus, G. erinaceus, is redescribed from Raja spp. in the eastern and western north Atlantic and the Mediterranean. The redescription establishes the presence of: an hermaphroditic sac; internal and external seminal vesicles (but absence of an accessory seminal vesicle); a uterine pore; and the attachment of the retractor muscle in the mid-region of the tentacular bulb. G. pseuderinaceus Dollfus, 1969 and G. recurvispinis Dollfus, 1969 from Raja spp. in the Mediterranean are considered to be synonyms of G. erinaceus, following Palm (2004). G. dollfusi Carvajal, 1971 from R. chilensis Guichenot off Chile is redescribed from the paratypes and features of the terminal genitalia, consistent with those of G. erinaceus, are described for the first time. G. musculara (Hart, 1936) is redescribed from new material collected from the type-host, R. rhina (Jordan & Gilbert), off Nanaimo on the western coast of Canada. The features of the terminal genitalia of G. musculara are similar to those of the G. erinaceus group. The morphological features of G. borealis Keeney & Campbell, 2001 from Bathyraja spp. in the Bering Sea and the Sea of Okhotsk are summarised and illustrations of this species provided. G. brayi n. sp. is described from Amblyraja radiata from the coasts of Iceland and Britain. The new species differs from other members of the complex in lacking modified hooks 1 and 1' at the base of the tentacle (differentiating it from G. erinaceus), a long pars vaginalis (differentiating it from G. dollfusi) and uncinate hooks in the band on the external surface of the tentacle (differentiating it from G. musculara). Brief descriptions are provided of two apparently new species of Grillotia currently represented in collections by single specimens.

Parallel, paedomorphic evolutionary processes of the bivalve-inhabiting hydrozoans (Leptomedusae, Eirenidae) deduced from the morphology, life cycle and biogeography, with special reference to taxonomic treatment of <i>Eugymnanthea</i>

It is hypothesized that bivalve-inhabiting hydroids originated from colonial, free-living eirenid hydrozoans, initially appearing as an Eutima species with solitary hydroids producing immature medusae with tentacles and manubrium, and also with derived characteristics of the marginal warts of the mature medusae as the remnants of the tentacular bulbs of the ancestral eirenid, and decreased number of statocysts. The derivate eumedusoid-producing Eugymnanthea evolved then. Deduced from the morphology, life cycles, and geographical distributions of this group and of all the known extant Eutima species, it is proposed that parallel, paedomorphic evolution took place in the marginal regions of the area of distribution of the ancestral-like Eutima at least in the northern hemisphere of both the Pacific and the Atlantic Oceans. Eugymnanthea appeared as a polyphyletic taxon as a result of the parallel evolution of different species of Eutima. It is pointed out that Eugymnanthea and Eutima are to be merged into a single genus in the future.

Patterns of electrical activity in comb plates of feeding Pleurobrachia (Ctenophora).

The electromotor behaviour of ciliary comb plates was studied during prey-stimulated and electrically stimulated feeding by intact Pleurobrachia pileus (Müller). Comb plate electrical activity was recorded by extracellular electrodes attached directly to the cilia; comb plate motility was recorded by high-speed video microscopy. Comb plate electrical activity fell into two distinct classes, identified by waveform and amplitude: (i) excitatory postsynaptic potentials (EPSPS) in the comb plate (polster) cells and (ii) regenerative potentials in the cilia, as described previously (Moss & Tamm 1987). Slow phasic bursts of regenerative potentials (reversal volleys) were observed in comb plates of rows undergoing reversed beating during capture of prey or by rhythmic electrical stimulation of the tentacles. All plates of a given comb row exhibited virtually identical electrical activity. Timing and development of electrical activity in comb plates of the subtentacular (ST) rows were nearly identical even though separated by several centimetres; onset of the reversal volleys of plates of subsagittal (ss) rows were delayed on average by about 0.5 s relative to the ST rows, although individual EPSPS displayed very similar timing. Microsurgery, combined with extracellular recording from comb plates and the tentacle and associated basal structures, revealed the presence of an integrative center in the tentacular bulb. This communicates with the comb plates by means of a diffuse pathway, presumably the nerve net, which itself is maximally sensitive to rhythmic input. The pathway underlying the reversal volley may innervate only the stimulated hemisphere. In addition to the rhythmic pathway, a through-conducting pathway runs from distal regions of the tentacle to the comb plate cells. Yet another excitatory pathway, possibly distinct from the tentacular through-conducting pathway, may mediate certain cases of global postsynaptic activity. The pathway that controls mouth movements during feeding is entirely independent of any comb plate pathway.

Physiology of obliquely striated muscle fibres withinGrillotia erinaceusmetacestodes (Cestoda: Trypanorhyncha)

SUMMARYThe tentacular bulb ofGrillotia erinaceusmetacestodes consists of obliquely striated muscle fibres with obvious motor end-plates. In this study isometric tension recordings and intracellular microelectrodes have been used to record mechanical and electrical activity from single isolated bulbs. Bulbs were mechanically quiescent and displayed resting membrane polentials (RMP) in the region of −49 to −64 mV with a mean RMP of −56 mV (n= 60). The membrane potential varied with [K+]oin a manner consistent with the RMP being determined largely by the K+equilibrium potential. High K+solution (> 15 mM) caused membrane depolarization and contraction of the preparation with the contraction showing both phasic and tonic components. L-glutamate caused membrane depolarization, contraction of quiescent preparations and increased the amplitude of electrically evoked responses. In contrast, 5-HT, dopamine, histamine, adrenaline, GABA, noradrenaline and D-glutamate, at concentrations up to and including 10−3M, were without apparent affect, although acetylcholine, at relatively high concentrations (≥ 10−4M) slightly reduced the amplitude of field-evoked contractions.

Ultrastructure of the rhyncheal system of Trimacracanthus aetobatidis (Cestoda:Trypanorhyncha)

The rhyncheal system of T. aetobatidis comprises the tentacle, tentacle sheath, tentacular bulb, retractor muscle and prebulbar organ. The tentacle is covered externally by an electron-dense lamina into which the hooks are inserted. Internally, a complex of fibrillar and vesicular layers is present with a few muscle fibres. The fibrillar sub-surface layers of the tentacle are continuous with the sheath, and the sheath persists as an outer coat to the bulb. The ultrastructure of the tentacle has homologies with the basal lamella of the scolex tegument and the two are probably continuous. The bulb is composed of vacuolated striated muscle fibres while the muscles of the retractor muscle and the somatic muscles are smooth. Numerous mucin-producing glands surround the retractor muscle. The prebulbar organ contains scleroprotein, no organelles, and probably has a mechanical function only.

Structure and ultrastructure of muscle systems within Grillotia erinaceus metacestodes (Cestoda: Trypanorhyncha).

Three distinct muscle types have been identified within the metacestode of Grillotia erinaceus. These consist of peripheral somatic myofibres plus two muscle systems directly involved in parasite attachment to the host, i.e. the tentacular bulb and its antagonistic retractor muscle. In common with other cestodes the somatic muscle consists of smooth-type fibres running longitudinally and obliquely to the main body axis. The retractor muscle consists of myofibres with centrally displaced nuclei. Upon contraction these latter fibres become spirally orientated causing the muscle to coil and lateral membranes to become elevated as spikes. Definitive nerve processes have not been identified within somatic or retractor muscle. Individual tentacular bulbs form the proximal terminus for a closed hydraulic system. Each bulb consists of overlapping, contrarotating myofibres which display obvious striations; the striations appear in alternate fibres to be in transverse and oblique planes. Adjacent myofibres are separated by approximately 0.5 micron, possess abundant mitochondria and have shallow t-tubules plus associated vesicles of sarcoplasmic reticulum at each Z line. Thick myofilaments are surrounded by 13, shared, thin myofilaments. Close neuronal control for the bulb muscle is suggested by the presence of obvious motor end-plates which contain both lucent and dense neurovesicles.

Surface morphology and description of Otobothrium kurisi new species (Cestoda: Trypanorhyncha) from a hammerhead shark, Sphyrna lewini

Shields J. D. 1985. Surface morphology and description of Otobothrium kurisi new species (Cestoda: Trypanorhyncha) from a hammerhead shark, Sphyrna lewini. International Journal for Parasitology 15: 635–643. Otobothrium kurisi new species is described from the scalloped hammerhead shark, Sphyrna lewini. Otobothrium kurisi is the third species of Otobothrium to be described with a villous peduncle. It can be distinguished from other closely related species by its elongate tentacular bulbs, with a bulb ratio of 1.8: 1, a moderately large scolex (1900–2720 μm), and a pars bothridialis to pars vaginalis to pars bulbosa ratio of 1: 2.8: 0.9. Scanning electron microscopy of the tegument of the scolex revealed minute, tripartite spines on the entire bothridial surface. The bothridial surface spines may aid attachment and indirectly aid in the absorption of nutrients. The peduncle of the scolex was villous; each villus in turn, possessed microtriches. The density of microtriches was compared to that of other species of tapeworms

Description ofRathkea lizzioidessp. nov. (Hydromedusae: Rathkeidae) from Antarctica and a key to the genus

A new species of hydromedusa from the Antarctic, Rathkea lizzioides sp. nov. is described and illustrated. The species is characterized by its rounded bell-shaped form, being almost as broad as high, the presence of an apical dome and a gastric peduncle, the 4 unbranched oral arms, the number of nematocyst clusters (7 to 18 in specimens 1·5 mm or greater in height), the occasional presence of 1 or more nematocyst clusters near the mouth margin, the 5 to 7 tentacles in each perradial tentacular bulb, the 3 to 5 tentacles in each interradial tentacular bulb, and the ovoid shape of the tentacular bulb. A key to the known species of Rathkea is provided.

OBSERVATIONS AND EXPERIMENTS ON THE PHYSIOLOGY OF MEDUSAE

1. Studies were made in Puget Sound on several medusae belonging to the groups Anthomedusae (Stomotoca, Sarsia), Leptomedusae (Aequorea, Halistaura, Phialidium), and Stauromedusae (Haliclystus).2. The water content was determined for four species (Aequorea, Halistaura, Phialidium, Sarsia) and found to range from 96.5 to 97 per cent (salinity of the sea water 3.09 per cent). Evidence was obtained that the water content declines slightly with increasing size.3. Activities are limited and responses cannot be elicited with dependable regularity.4. All species observed have alternate periods of pulsation and floating; in general these periods bear no absolute or relative time duration to each other.5. Behavior is correlated with morphology and hence shows characteristic differences between the different groups.6. Mechanical or chemical stimulation, when effective, elicits either an escape reaction or the feeding reaction.7. The escape reaction may consist of bell pulsations but to stronger stimuli a general contraction, termed crumpling, accompanied by cessation of swimming, is given. Aequorea is anatomically incapable of this escape reaction because of its thick stiff bell.8. The feeding reaction consists in the Leptomedusae and Haliclystus of bending the stimulated region of the margin to the manubrium which also moves to meet the inbent margin. In the Anthomedusae it consists of turning the long manubrium in the direction of stimulation.9. Food was traced through the gastrovascular system by feeding bits of animal flesh coated with carmine. Within half an hour after feeding, food begins to spread along the radial canals and in two or three hours occupies the entire gastrovascular system.10. The principal sites of intracellular digestion are the lining epithelium of the manubrium, stomach, and tentacular bulbs. Radial, circular, and tentacular canals play a minor rôle. Those portions of the radial canals adjacent to gonads (Leptomedusae) are much more active in intracellular digestion than radial canals elsewhere.11. No definitely directed flagellar currents could be observed in the gastrovascular system.12. Strands of carmine-containing mucus were seen to be extruded from the so-called excretory pores of the radial canals (Aequorea).13. The fluid from the stomach of Aequorea is usually considerably more acid than sea water (to pH 7.2, mostly 7.4-7.6). It contains a proteolytic and a lipolytic enzyme but appeared to be devoid of diastases.14. Feeding and escape reactions of Haliclystus (a sessile stauromedusan) are similar to those of Leptomedusae. No function could be found for the anchors; the animal gave no response to chemical or mechanical stimulation of the anchors nor were they used for adhesion.15. The tentacular bulbs of hydromedusae function as depots for the manufacture and storage of nematocysts, as organs of general sensory perception, and as important sites of intracellular digestion. They are not photoreceptors although in Anthomedusae they bear the ocelli when these are present. The tentacular bulbs of Gonionemus are devoid of differentiated photoreceptors.

On the First Stage of the Medusa Eucheilota Clausa (Hincks)[= E. Hartlaubi Russell

In the last number of this Journal (Russell, 1936) I described under the name Eucheilota hartlaubi the adult and various stages of a medusa that is fairly common in the Plymouth plankton but had up till then remained undescribed. This medusa was identified with an unnamed medusa which Hartlaub had figured as having been reared from the hydroid Lovénella clausa Lovén.On March 10th, 1936, some Lovénella clausa kept in this laboratory by Mr. W. J. Rees liberated medusæ. Mr. Rees kindly handed these over to me so that I could follow the early development. When first liberated the medusa was conically bell-shaped (Fig. 1) and there were scattered nematocysts on the exumbrella. There were two fully developed opposite perradialtentacles, and two non-tentacular perradial bulbs. Rudiments of spiral cirri were developing on either side of the tentacular bulbs. There were four interradial marginal cirri each of which was situated on the umbrella margin about midway between the tentacular and nontentacular bulbs.On the tentacle sides of each of these marginal cirri was a marginal vesicle with a single concretion. The medusa was 0.75 mm. high by 0.75 mm. broad. The colour of the tentacular and non-tentacular bulbs and the stomach was pale straw. By the next day the umbrella had assumed amore oval bell-shape and the colour of the bulbs and stomach was now a bright orange-yellow. OnMarch 12th the medusa was now 0.9 mm. high and the rudiments of cirri were developing on one side of each non-tentacular bulb (Fig. 2).