262 SUMMARY OE CURRENT RESEARCHES RELATING To 



The mouth can be completely closed. The gonads were poorly 

 developed in all the specimens, most of which seemed to he males. 

 The tentacles varied from 85 to 110. The nettle-ring is comparatively 

 narrow, but is thickened and folded round the bases of the tentacles, the 

 thickenings resembling the tentacle-buds of other Medusoids. In an 

 individual with !>G tentacles, 84 sense-organs were counted — a pair at 

 the base of each of the larger tentacles near the velar margin of the 

 nettle-ring, whilst a single sense-organ occurs in a similar position at 

 the base of each of the other tentacles with the exception of the smallest, 

 which are without these organs. The Medusoids were infested with a 

 peritrichous infusorian (Trichodina). 



Fresh-water Hydromedusoid.* — The late George du Plessis found 

 in August 1912 a number of Medusoids in fresh-water near St. Raphael. 

 They occurred in a lagoon of clear water (called le petit Argens), com- 

 municating with the Argus, a stream which enters the sea opposite 

 Frejus. The smallest were of the size of a pin's-head ; the sexual 

 adults as large as a " dix-sous " piece. Du Plessis referred them to the 

 genus Laodice, which is represented in the Mediterranean by several 

 littoral species. 



The winter is spent attached to green Algre ; the free life begins in 

 April. The ovaries lie along the radial canals. The fertilized ova give 

 rise to ciliated planulas, and these become in a few hours very minute 

 hydroid polyps, which may be sedentary or may float at the surface of 

 the water. 



The polypoid form remains single without forming a colony. It has 

 irregularly disposed tentacles. In two or three days it buds off minute 

 medusoids with four tentacles. These medusoids grow and increase the 

 number of their tentacles, become sexual, and liberate planulae. It is to 

 be regretted that the observations made by Du Plessis were not left in a 

 form available for publication. 



Porifera. 



Gametogenesis of Grantia compressa.f— Arthur Dendy finds that 

 this sponge is hermaphrodrite, producing ova and spermatozoa simul- 

 taneously, but that the spermatozoa are produced in comparatively 

 small numbers, the minute sperm-morulas being scattered here and there, 

 enclosed in spermatocysts, between the collared cells of the chamber 

 walls, and also occurring free in the flagellate chambers. The spermato- 

 gonia in these sperm-morula3 are extremely minute, and their mode of 

 division was not observed. Apparently they are sometimes transferred 

 as sperm-moruhe to the inhalant canals of the same or of another 

 individual, where they break up into spermatozoa, but it is probable that 

 they may sometimes break up into spermatozoa before leaving the parent 

 sponge. The evidence on these points is, however, curiously scanty, and 

 it seems that the spermatozoa are rarely, if ever, liberated in large 

 numbers. The evidence goes to show that Grantia compressa is normally 



* Proems- Verbaux Soc. Vaud. Sci. Nat., 1. (1914) pp. 62-3. 

 t Quart. Journ. Micr. Sci., lx. (1914) pp. 313-76 (4 pis.). 



