OF THE VERTEBRATE OVARY 609 



though there are no investigations as to the changes undergone 

 by the nucleus in other types, still it appears to me safe to con- 

 clude that the results arrived at hold good for Vertebrates 

 generally 1 . As has already been pointed out the transformation 

 which the so-called primitive ova undergo is sufficient to shew 

 that they are not to be regarded as ova but merely as embryonic 

 sexual cells. A feature in the transformation, which appears to 

 be fairly constant in Scyllium, and not uncommon in the rabbit, 

 is the fusion of the protoplasm of several ova into a syncytium, 

 the subsequent increase in the number of nuclei in the syncy- 

 tium, the atrophy and absorption of a portion of the nuclei, and 

 the development of the remainder into the germinal vesicles of 

 ova ; the vitellus of each ovum being formed by a portion of the 

 protoplasm of the syncytium. 



As to the occurrence of similar phenomena in the Vertebrata 

 generally, it has already been pointed out that Ed. van Beneden 

 has described the polynuclear masses in Mammalia, though he 

 does not appear to me to have given a complete account of their 

 history. Gotte 2 describes a fusion of primitive ova in Amphibia, 

 but he believes that the nuclei fuse as well as the bodies of the 

 ova, so that one ovum (according to his view no longer a cell) 

 is formed by the fusion of several primitive ova with their 

 nuclei. I have observed nothing which tends to support Gotte's 

 view about the fusion of the nuclei, and regard it as very im- 

 probable. As regards the interpretation to be placed upon the 

 nests formed of fused primitive ova, Ed. van Beneden maintains 

 that they are to be compared with the upper ends of the egg 

 tubes of Insects, Nematodes, Trematodes, &c. There is no 

 doubt a certain analogy between the two, in that in both cases 

 certain nuclei of a polynuclear mass increase in size, and with 

 the protoplasm around them become segmented off from the 

 remainder of the mass as ova, but the analogy cannot be pressed. 

 The primitive ova, or even the general germinal epithelium, 

 rather than these nests, must be regarded as giving origin to the 

 ova, and the nests should be looked on, in my opinion, as con- 



1 Since writing the above I have made out that in the Reptilia the formation of 

 the permanent ova takes place in the same fashion as in Elasmobranchii and Mam- 

 malia. 



" EntwickltatgtgticMckU d. L Xv. 



