374 SUMMARY OF CDKRENT RESEARCHES RELATING TO 



the abdominal cavity of fresli-water iislies, than to any other species, 

 and without asserting positively that it may not be a variety of that 

 form, the author thinks, from the unique character of its habitat 

 associated with certain differences of form, that it may properly 

 be regarded as the immature rejjresentative of a totally distinct 

 species. 



Echinodermata. 



Psolus and its Allies.* — Prof. F. Jeffrey Bell, after giving the 

 reasons which justify the use of the name Psolus as against Ciwieria, 

 and a list of the known species and well-established synonyms, 

 proceeds to give some account of some of the forms of that genus 

 of Holothurians. He finds that in Psolus fabricii the yoimger 

 are more strongly imbricated than older specimens, and that the 

 species has a circumpolar distribution, being found in the Japanese 

 seas. A new subgenus — Hypopsolus — is formed for a specimen 

 remarkable for having a comparatively small number of covering 

 plates which are invested in a thick integument in which there 

 are some calcareous deposits. Psolus {Hypopsolus) amhulator is 

 found in the Australian seas. He finds that the Polian vesicle is 

 not, as might have been supposed, better developed in the more 

 heavily than in the less heavily armed species, and he concludes 

 that, for the purposes of systematic zoology, it is most convenient to 

 recognize three sub-genera — Psolus S. Str. (Eiipsolus) with granular 

 plates, a median row of trivial suckers, and no basal web to the 

 tentacles ; Lophotlmria with large granulated plates, no median row, 

 and a basal web ; while Hypopsolus has a very rich supply of trivial 

 suckers and the scales invested in a thick integument. 



Perivisceral Fluid of the Sea-TJrchin.t— Prof. E. A. Schafer finds 

 that if the perivisceral fluid of an Echinus, which has about the same 

 specific gravity and chemical composition as sea-water, be drawn from 

 the " shell " it rapidly undergoes what appears to be a sort of coagula- 

 tion ; this coagulation now shrinks until it is reduced to a small shred of 

 coloured substance, and in this resjiect it closely resembles that of 

 vertebrate blood. Examined with the Microscope, the clot is found 

 to contain all the corjiuscles, and these are so closely arranged and 

 their processes are frequently so long and ramified, that it is difficult 

 to make out the material in which they are imbedded. This material 

 has been overlooked by Geddes, but by experiment it is possible to 

 see that there is a clear substance in which the corj^uscles are im- 

 bedded ; this coagulable material does not appear to be fibrine, but to 

 be a body more nearly allied to mucin, " although the possession by 

 it of the remarkable property of spontaneously shrinking after its 

 first formation gives it a deceptive similarity to fibrine." The author 

 promises a more detailed account of his investigation. 



* Proc. Zool. Soc., 1882, pp. 641-50 (1 pi.). 

 t Proc. Roy. Soc, xxxiv. (1883) pp. 370-1. 



