OVAEY AND OVARIAN OVA IN CERTAIN MARINE FISHES. 123 



spermatocytes. The question of the occurrence of direct or 

 amitotic division in tlie multiplication of germ-cells is dis- 

 cussed by O. vom Rath, in a paper published in 1894' (13). 

 He states that many authors consider that this mode of 

 division occurs in genital cells. He points out that a decision 

 of the controversy is of great importance, since all modern 

 views on the nature of fertilisation and heredity are based 

 on the assumption of the continuous succession of mitotic 

 or indirect divisions in the history of genital cells. He 

 argues that if amitotic division did take place, an exact 

 division of the chromatin between the two daughter-cells 

 would be impossible, since the division of the threads does not 

 occur in that process as it does in mitosis. Nevertheless, vom 

 Rath has himself seen phases of amitotic division in genital 

 cells in the ovary of the Salamander, especially in very young 

 females, together witb stages of regular mitosis; in his figure, 

 however, he shows none of the latter. He considers that 

 all the ova or germ-cells which undergo amitotic division 

 are abortive, are undergoing retrogressive changes, and are 

 about to be absorbed. In the ovaries of older specimens 

 of Amphibia, amitosis is more seldom seen, but degeneration 

 of ova without amitosis is common. Vom Rath considers 

 that the amitoses observed by other investigators in generative 

 organs were in many cases divisions of follicular cells, which 

 come to an end of their history when the genital cells are ripe or 

 are absorbed, and not of true germ-cells destined to become 

 ova or spermatozoa. In fact, he maintains the general theory 

 that amitosis only occurs in cells which are approaching the 

 termination of their capacity for division, and that when 

 amitosis of the nucleus once occurs nonfe of its descendants 

 ever again pass through the processes of mitosis, but soon 

 cease to divide at all, and ultimately die. Mitosis is, accord- 

 ing to this view, essentially connected with the continuity and 

 persistence of cell life. 



The youngest stage of the Teleostean ovary which I have 

 examined is that of a plaice 3 inches long. The specimen was 

 killed in March, and must have been hatched in the previous 



