126 The Ottawa Naturalist/ [Oct. 



in an extreme case, finally quit the ovigerous capsule."* Koren 

 and Danielsson in 1857 studied the eggs of the large whelk 

 (Buccinum) and decided that many eggs united to form one 

 large embryo, the remaining eggs dying and breaking up; but, 

 immediately after the publication of the Danish observers' views, 

 Dr. Carpenter gave the correct account of the strange phenom- 

 enon, an account supported by the later researches of Dr. 

 Dyster. Part of the eggs are fertilized and part are not ferti- 

 lized but are devoured by the former while still contained in 

 the capsule. Long before the infant mollusks become active 

 "veligers." or free-swimming larvae, with a crown of waving 

 cilia, they turn cannibal. Dr. Carpenter noticed that some 

 larvae did not devour their fellows; but depended for nutriment 

 upon their own stock of volk-macromeres. These became 

 stunted, and many died. The macromeres, it is hardly necessary 

 to say, are the large segments at one side of the egg, as dis- 

 tinguished from the micromeres at the other side, the latter form- 

 ing the germ. Selenka confirmed Dr. Carpenter's results but 

 held that the cleavage of the early unfertilized egg was not true 

 segmentation, and inferred that, while the minute features of 

 the yolk, in both kinds of eggs, appeared to be the same, there 

 was no nucleus discoverable in the unfertilized eggs. In the 

 Gastropod Tergipes ansea he found that when this irregular 

 segmentation took place, portions of the volk were thrown off, 

 developed cilia, and became independent moving " cosmellas," 

 as Von Nordmann called them, and they have been regarded as 

 parasitic in nature. Edouard Clapareda, again, from his study 

 of Neritina fluviatilis w'as able to further confirm Carpenter, and 

 Blochmann discovered, in the same small fresh- water shellfish, 

 that one embryo only may survive out of 70 or 80 contained 

 originally in one capsule. Dr. W. K. Brooks announced, more 

 recently, that in the egg-case of Urosalpinx, containing six to 

 twenty ova, many of them are devoured by the others both in 

 the earlier and the later stages of embryonic development. 

 Professor J. P. McMurrich, of Toronto, has confirmed these last 

 results by a study of Crepidula and Purpura floridana, finding 

 that a number of eggs always break down or disintegrate to 

 serve as food for their surviving brethren. In Fasciolaria tulipa, 

 one of the Muricidae, he noted that four, or five, or six, embryos 

 may ultimately emerge from one nidamental capsule, which 

 originally contains about two hundred eggs. But not only in 



*Haacke has stated that in certain AustraUan Rays (Tryogorhina 

 and Rhinobatis) more than one ovum is contained in one homy capsule, 

 and Dr. Otto Klotz, of Ottawa, brought the same fact to my attention 

 in the huge British -Columbia skate (Rata cooperi, Gir.) 



