APLYSIA. 253 



forming an orange or pink tangled mass on or around the weed. 

 Deposition usually takes place at night in the aquarium. The 

 number of eggs in a single cordon is always very large. Fischer 

 measured an egg string eighteen metres in length, and estimated 

 that it contained about 108,000 eggs. Relatively few of these, 

 however, will reach maturity. In addition to the hazards of a 

 pelagic larval period and of the metamorphosis, the spawn is 

 often eaten by Crustacea, and it is said that Aplysia itself 

 will consume its own mutilated egg strings. 



The account given above of the function of the spermato- 

 cyst and spermatheca agrees in the main with that described 

 by Eliot for Doris, where the genital apparatus is triaulic and 

 therefore less complicated. It differs from the description 

 given by Mazzarelli and by Guiart of the reproductive apparatus 

 of Aplysia. Mazzarelli* did not find the connection between 

 the external seminal groove and the little hermaphrodite 

 duct, but states that the sperms pass out by the oviduct. 

 He describes the penis as being directed by a fold so that the 

 sperms enter the spermatheca, whose function is to purify 

 the sperms from extraneous matter. The sperms, he says, 

 then pass in the pure condition to the spermatocyst. The 

 above description shows, however, that the sperms pass out 

 by a continuous groove from the little hermaphrodite duct 

 to the external seminal groove, and examination of large 

 numbers of individuals immediately after copulation revealed 

 only a negligible quantity of sperm in the spermatheca, and 

 pure sperm, in an active condition, in the spermatocyst. 



Guiart,t on the other hand, homologises the spermatocyst 

 of Aplysia with that of other Opisthobranchs, and says that it 

 is a true vesicula seminars and does not open into the vagina. 



* Mazzarelli, G. " Monografia delle Aplvsiidae del Golfo di Napoli." 

 Mem. Soc. Ital. Scienze, 3, IX, 1893, p. 120. 



t Guiart, J. " Contributions a 1' etude des Gasteropodes Opistho- 

 branches et en particulier des Cephalaspides." Mem. Soc. ZooL, France, 

 1901. 



