OVARY AND OVARIAN OVA IN CERTAIN MARINE FISHI']S. 141 



chromatin network, althougli distinct and well stained, is so 

 dense, and exhibits so many crossings in all directions, that it 

 appears to have the structure characteristic of the resting 

 nucleus. He declares, however, that by means of the oil- 

 iramersion lens he was able to resolve the network into a 

 tangle (knauel) of chromosomes, and that in thin sections of 

 the germinal vesicle some of these being included in their 

 whole length can be seen to be double. He was even able to 

 see traces of doubling in the daughter tangles of the last 

 mitotic division of the germ-cells, and comes to the conclusion 

 that the germinal vesicle in the egg during its enlargement 

 and growth is not a resting nucleus, but a daughter tangle of 

 the germ-cell enlarged to enormous dimensions. 



The history of the germinal vesicle in Teleostean ova, 

 according to my observations, agrees in many respects with 

 that described by Riickert in Selachians. There are certain 

 well-known features which are common to both cases, in 

 particular the conspicuousness and deep staining of the nu- 

 cleoli, and the indistinctness and unstained condition of the 

 nuclear network during a considerable period of the egg's 

 growth. As I have already described, in the smallest ova in 

 my preparations, about '01 mm. in diameter, the germinal 

 vesicle exhibits one large conspicuous nucleolus, with others 

 much smaller, and a nuclear network. The structure of these 

 germinal vesicles or nuclei appears to resemble that of a resting 

 nucleus in an ordinary cell, and 1 have not been able to dis- 

 tinguish chromosomes in them as described by Riickert in the 

 ovum of Selachians. I cannot assert that the network does 

 not consist of separate chromosomes, but although I have used 

 sections from material fixed in Flemming's mixture, and have 

 studied them with an apochromatic oil-immersion of 20 mm. 

 by Zeiss, I have not succeeded in resolving the network into 

 chromosomes. Riickert maintains that with sufficient magnify- 

 ing power and careful scrutiny the apparent network can 

 always be seen to consist of a tangle of chromosomes, and 

 that the germinal vesicle is, in fact, an enormously enlarged 

 tangle-phase or spirem, and therefore essentially different from 



