OVAEY AND OVARIAN OVA IN CERTAIN MARINE FISHES. 127 



spond to the stroma of the ovary containing definite ova, and 

 not to include the germinal epithelium properly so-called. 



G. Born (7) mentions briefly that in the ovary of Triton 

 toeniatus, between the larger eggs are primitive ova^ or nests 

 of them; that he often saw in these primitive ova stages of 

 mitosis, and that he also saw lying in contact with the resting 

 nuclei of primitive ova a mass of finely granular protoplasm 

 containing some more distinct granules. But he gives no 

 further consideration to these points, his paper being devoted 

 to the later history of the ovum. 



R. Pick (10) and Ruckert (8) also confine themselves to the 

 discussion of the history of the definite ovum after it has left 

 the germinal epithelium and ceased to divide. 



I have not been able to trace the centrosome in the primitive 

 ova still within the germinal epithelium, nor have other ob- 

 servers described it in this stage in Teleosteans. It is still a 

 disputed point whether the centrosome is a permanent organ 

 of the cell, that is to say whether it is always present in the 

 cytoplasm throughout all the successive phases of cell-life, 

 dividing before the nucleus when division takes place. The 

 majority of authors believe in the persistence of the centro- 

 some, and hold that it is always outside the nucleus. But 

 O. Hertwig maintains that this is true only in certain cases, 

 and that usually after mitosis the centrosome passes into the 

 interior of the nucleus, and only emerges again into the proto- 

 plasm when the cell is preparing to divide again. 



Beneath the epithelium in the ovarian lamellae in these 

 sections is a layer of young ova, all destitute of yolk, of 

 various sizes, the largest being '14 mm. in diameter. In the 

 larger of these the vitelline nucleus is very definite and con- 

 spicuous, forming a rounded or elliptical body, somewhat 

 deeply stained and having a granular appearance. Sometimes 

 the granular appearance is seen to be due to vacuoles, and 

 occasionally I have fancied I saw a minute corpuscle in the 

 centre of the mass. As usual, the edges of the body are not 

 sharply defined, but are seen to be connected with the strands 

 of the surrounding cytoplasm. In the smaller eggs there is 



