138 LACINULARIA SOCIALIS 



be said — i. That the sexes are united in most Distomata, for instance, 

 and separated in species closely allied (e.g. D. Okenii). 



2. That the differences between these bodies and the spermatozoa 

 of Notonuiiata is not greater than the difference between those of 

 Triton and those of Rana. 



3. That their development from nucleated cells within the body of 

 Megalotrocha (teste Kolliker) is strong evidence as to their having 

 some function to perform ; and it is difficult to imagine what that can 

 be if it be not that of spermatozoa. However, it seems to me 

 impossible to come to any definite conclusion upon the subject at 

 present.^ 



Kolliker supposes that Ehrenberg has seen the " spermatozoa," 

 and has taken them for the " long vibratile bodies " ; while Siebold 

 imagines that Kolliker has taken the long vibrating bodies for 

 spermatozoa. No one, however, who has seen both structures can be 

 in any danger of confounding the one with the other. 



Asexual propagation of Laciiiularia. — Whatever may be the nature 

 of the process of reproduction just described, there exists another 

 among the Rotifera, which has been noticed by almost every one, but 

 not hitherto distinguished or understood. This is the production of 

 the so-called " winter ova," but which from their analogy with what 

 occurs in Daphnia, I prefer to call " ephippial ova." 



Ehrenberg says that many ova of Hydatina have a double shell, 

 and between the two shells there is a wide space. " Similar ones 

 occur in many Rotifera, in various often irregular forms : these have a 

 much slower development, and I call them thence winter ova" (p. 413). 

 See also his account of Brachionus urceolaris (p. 512). He does not 

 notice the occurrence of these ova in Lacinularia or Megalotrocha. 



Kolliker speaks of the ova of Megalotrocha acquiring a deep 

 }'ellow investment, as if it were a further development of those ova 

 whose yolk he saw divided. I am strongly inclined to believe, however, 

 that he was misled by the peculiar appearance of the winter ova 

 which look as if they had undergone yolk division. 



Dalrymple gives a lengthened account of these peculiar ova in 

 Notoiiunata. He says that they are dark, and that their outer cover- 

 ing appears to consist of an aggregation of cells, under which is a 

 second layer of cells containing pigment molecules. No distinct 

 germinal vesicle, he says, is to be found in these ova " from the want 

 of general transparency " {loc. cit. p. 340). 



' I may mention here that I have found in Melicerta an oval sac lying below the ovary, 

 and containing a number of strongly-refracting particles closely resembling in size and form 

 the heads of the spermatozoa of Lacinularia. 



