6 ralph e. wagek. 



Growth of the Egg. 



The germinal area having been formed as above described, the 

 egg begins its growth. Near the center of the mass of primitive 

 ova there are to be found several which are larger than the rest. 

 These cells lie close to the supporting membrane. Downing 

 ('08) is inclined to regard these cells as the true ova, and is of 

 the opinion that they are always present and recognizable among 

 the interstitial cells of the adult animal. He notes that there are 

 some cells which are spherical in outline, and are possessed of 

 a very large nucleus near which there lies a small dark ovoid 

 body. As noted above, the interstitial cells even in an early 

 stage in the formation of the germinal area, differ considerably in 

 size. The ovoid bodies near the nucleus are to be found in 

 many of the interstitial cells lying near the supporting layer, and 

 are doubtless only a metaplasmic body. It is permissible, cer- 

 tainly, to regard these cells as ova, and, as Downing contends, 

 as true ova, but it would seem to be impossible to show that 

 these large cells do not have precisely the same origin as the re- 

 maining ones of smaller size over which they have an advantage 

 by virtue of their nearness to the entoderm from which their food 

 supply is derived. All stages, as regards size, are to be found 

 between these large and even the smallest cells. Unless these 

 large cells do have a different origin than do the small ones, or 

 unless they become markedly different in some respect from the 

 small ones, there is nothing to be gained by regarding them as 

 true egg cells and the small ones, therefore, as something entirely 

 different. That these large cells may be present in the ectoderm 

 is doubtless true. That the egg, in the manner to be described, 

 takes its rise always from these and no other later formed large 

 cells, seems to me to be extremely improbable. 



The processes concerned with the growth of the egg are inter- 

 esting. Tannreuther ('08) has already pointed out that the egg 

 mass originates by the coalescence of a number of the primitive 

 ova, the process beginning in the large cells near the center of 

 the ovarian area. Inasmuch as my own observations were carried 

 on in somewhat greater detail, it may be justifiable to outline the 

 process again. 



Reference has already been made to the large cells which, 



