590 SUMMARY OF CURRENT RESEARCHES RELATING TO 



physiology and histology, in which certain physiological observations 

 of the latter author are included. As to physiology, Berger finds that 

 Charybdea is very sensitive to strong light, which, like total darkness, 

 inhibits the pulsations, while moderate light acts as a stimulus. In this 

 respect it resembles a Hydromedusan, but in the temporary paralysis 

 and subsequent recovery after removal of the marginal bodies it re- 

 sembles a Scyphomedusan. In regard to histology, the most important 

 of the results obtained have reference to the structure of the retina of the 

 eyes of the sensory clubs. The retina of the distal eye contains two 

 kinds of sensory cells (the prism and pyramid cells), and long pigment- 

 CjIIs. The sensory cells contain an axial nerve-fibre which is probably 

 continued into the sub-retinal nerve-tissue. Iu the proximal eye prism- 

 cells only are present. In the simple eyes which occur in pairs at the 

 sides of the sensory clubs the retina consists of flagellated cells whose 

 flagella are continued into nerve-fibres. In both the simple and the 

 complex eyes the nerve-fibres display a dumb-bell-shaped basal body at 

 their point of entrance, least obvious in the case of the pyramid cells. 



Nematophores in Plumularidse.* — F. v. Pau singer has studied the 

 structure aud function of these organs in Acjlaophenia pluma and Plumu- 

 laria halecioides. He finds that in the former the nematophore is 

 divided at its distal end into an outer portion bearing stinging-cells, the 

 cnidostyle, and an inner freely movable portion, the sarcostyle. An 

 endodermic axis is present in both regions. The sarcostyle is able to 

 spread itself out freely over the colony, and can also put out pseudo- 

 podial prolongations. In Plumularia no distinction into cnidostyle 

 and sarcostyle can be observed, the whole nematophore contains stinging- 

 cells, and is freely movable, putting out pseudopodia and then retracting 

 these again. Further, under certain conditions the nematophore dis- 

 plays a gastric cavity, which either disappears again or unites with the 

 hydranth. As to morphological significance, the author believes that 

 the nematophore is to be regarded as a reduced individual characterised 

 by the great motility of the ectoderm ; he further considers the condition 

 in Plumularia halecioides to be the more primitive. In Plumularia 

 diaphana he finds that there is a functional distinction into cnidostyle 

 and sarcostyle, but not a morphological one, so that the condition may 

 be regarded as intermediate between that of Plumularia halecioides and 

 that of A<jlaophcnia pluma. As to function ; — in branches full of vitality 

 this appears to consist chiefly in keeping the colony free from parasites 

 or noxious bodies, a function accomplished by means of the great 

 motility. In degenerating parts of the colony the nematophores appear 

 to assimilate the substance of the dying polype for the benefit of the 

 remainder of the colony, aud also close the channel of communication 

 between the exterior and the coenosaic which would otherwise be left at 

 the death of the polype. 



Neocomian Coral from King Charles Land.f — If err G. Lindsfcrom 

 describes Tliecocyathus nathorsti sp. n., a Turbinolian coral from King 

 Charles Land, situated east of Spitzbergen. No other corals but these 

 were found there. He compares it with the other species, which can 



* Arbeit. Zool. Inst. Wien, xii. (1900) pp. 301-34 (3 pis.). 



t Ofvers. k. Veteusk. Ak. Forbaudl., lvii. (1900) pp. 5-12 (8 figs.). 



