576 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Sepia officinalis.* — L. Cu6not discusses the species Sepia officinalislj., 

 which seems at first sight very homogeneous and constant. It is in 

 reality a species in process of dissociation. Four forms may be distin- 

 guished — filUouxi Lapont, fischeri Lapont, officinalis, and veranyi 

 P. Fischer, which are incipient or nascent species. They differ from 

 one another (1) in the time at which they leave the medium depths of 

 the ocean to enter the waters of less depth and less salinity ; (2) in the 

 time of sexual maturity and oviposition ; and (3) in minute features of 

 form, such as the structure of the sepiostaire. 



y. Gastropoda. 



Gymnosomatous Pteropods of Coasts of Ireland.f — Annie L. 

 Massey reports on a collection of these minute animals from the west, 

 south, and east coasts ■ of Ireland. To distinguish nearly alhed species 

 it is often necessary to dissect out the buccal parts and prepare the 

 radula and hook-sacs. Of the twelve species dealt with six appear to be 

 new to science, and four have not previously been recorded from 

 British and Irish seas. The only form abundant enough to be of value as 

 fish food is Pneumodermopsis paucidens (Boas), which resorts chiefly to 

 shallow water. A key is given for the identification of -British and 

 Irish Gymnosomata. The new species are : — Pneumodermopsis oligocotyla, 

 Spongeohranchsea polycotyla, Clionopsis longecirrata, Cephalobrachia 

 bonnevii, Thliptodon atlanticus, and T. rotundatus. 



Sex-cycle in Crepidula.f — Harley N. Gould has studied the sexual 

 cycle of Crepidtda plana, which lives attached to the inside of the 

 Gasteropod shell occupied by the large hermit-crab, Eupagurits hern- 

 hardiis. It is a protandric hermaphrodite, with the male and female 

 phases completely separated. The assumption of the male condition 

 does not always occur at the same stage in the life-history, with respect 

 to age or size ; and there is reason to believe that the male phase is 

 sometimes entirely omitted. The growth of the animal during the first 

 part of its life, i.e. during the period in which male development may 

 occur, is very variable, and depends in part upon (1) the amount of 

 movement of the animal ; (2) the amount of space available for the 

 extension of the mantle ; and (3) the season of the year. 



Primordial male and primordial female cells are both present in the 

 gonad at the periods from the post-larval up to the adult female phase, 

 and are visibly different from each other. As in other protobrancbs there 

 are atypical as well as true spermatozoa. The former are of the 

 " apyi-ene " variety. They develop from cells which cannot at present 

 be distinguished from spermatogonia. After the cells, which are to 

 form apyrene spermatozoa, are differentiated, there are no maturation or 

 other divisions. 



During the change from the male to the female condition part of the 

 testicular cells complete their development and are passed into the 



* Arch. Zool. Exp6r., Ivi. (1917) pp. 315-46. 



t Sci. Proc. R. Dublin Soc, xv. (1917) pp. 223-44 (1 pi.). 



X Journ. Bxper. Zool., xxiii. (1917) pp. 1-69 (85 figs.). 



