130 .1, T. CUNNINGHAM. 



position as tlie nucleulij as iii these sections it has taken a 

 very different colour in staining. In none of my sections of 

 ovaries ofSyngnathus are the germ-cells sufficiently differen- 

 tiated to enable me to trace the centrosome in them_, or decide 

 as to the origin of the vitelline nucleus. 



Henneguy(ll)has recently studied thevitelline nucleus in the 

 ova of Teleosteans and other classes of Vertebrates. In young 

 ova of the trout he finds it is a round body at some distance 

 from the germinal vesicle, and consisting of a central part 

 deeply stained, and an external zone in whicb- the stain is less 

 intense. In Syngnathus acus he finds its earliest condition 

 in very young ova is that of a refringent corpuscle in contact 

 with the germinal vesicle. In his text he does not connect 

 the structure with anything previously existing in the germ- 

 cells either in a state of division or in the resting state, but 

 concludes that it arises from the germinal vesicle, and gives to 

 it a very far-fetclied and fanciful interpretation — namely, that 

 together with the nucleoli of the germinal vesicle, it repre- 

 sents the macro-nucleus of the Infusoria, the chromatic net- 

 work representing their micro-nucleus. But Henneguy gives 

 a figure of a section from the ovary of a newly- born kitten 

 which goes far to prove the identity of the vitelline nucleus 

 with the centrosome. At the time he wrote his paper, Bal- 

 biani's paper (12) mentioned below was not published, and the 

 doctrine of the centrosome was not so far developed as it has 

 been since. It is not surprising, therefore, that the author 

 overlooked the significance of the figure to which I refer. 



In this figure are shown germ-cells in process of mitosis 

 with a centrosome at each end of the spindle, and others in 

 the resting-stage with a minute stained corpuscle at the side 

 of the nucleus. There is nothing to distinguish this corpuscle 

 from the centrosome of the dividing cell on the one hand, and 

 on the other from the vitelline nucleus or corpuscle shown in 

 other figures of the same plate in ova contained in definite 

 follicles, except that the vitelline nucleus is somewhat larger. 



The history of the structure has also been studied by Mr. 

 Jesse W. Hubbard (15) in the ova of Cymatogaster aggre- 



