348 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Danielssen, little groups of eggs, containing from 30- 

 60, sometimes even 130 individuals, separate out, and 

 around them a delicate granular mass appears — a 

 supposed exudation from the eggs. Each little group of 

 eggs becomes an embryo, and the granular mass takes on 

 the form of a definite limiting membrane, which gives 

 later the shape of the larva. 



What really happens, however, is the much more 

 probable sequence observed first by Carpenter in 

 Purpura lapillus. According to this investigator, only 

 a few of the eggs in a capsule are to be looked upon as 

 true ova. The remainder are termed " yolk spherules." 

 The distinction between the two is manifested at the time 

 of the first segmentation, the yolk spherules dividing 

 into two equal hemispheres, the real ova into a larger 

 and smaller segment. Segmentation of both takes place, 

 however, and it should be interesting to determine 

 whether this is due to an actual difference in the eggs laid 

 or to fertilisation by the different kinds of spermatozoa 

 now known to exist. As the embryos develop they 

 commence actually to swallow the segmented yolk 

 spherules, and it is these carnivorous embryos which 

 Koren and Danielssen took to be clusters of eggs with an 

 exuded membrane. 



Bobretzky describes in some greater detail the 

 embryology of a gastropod supposed to be Fusus (sp. ?) 

 Whilst, however, he gives in his account a description 

 of the formation of blastula, gastrula, and early 

 embryonic stages, he does not make any mention of the 

 carnivorous act, and his egg capsules only contained 

 7-20 eggs ! The egg divides into two similar halves, 

 and then into four large cells by a second division. 

 These four large cells cut off four small ones which lie 

 close together. Four other small cells follow these, being 



