192 MUNSON. [Vol. XV. 



when the increased size of the cell and its nucleus shows it ta 

 be a growing egg (PI. XIV, Figs. 34, 38-40). It consists, in 

 this early stage, of two concentric circles of microsomes — a 

 large outer circle and a smaller inner circle. In the center of 

 the smaller inner circle is a granule, which at first hardly 

 exceeds in size one of the microsomes of the surrounding cir- 

 cle. The microsomes of each circle appear to be connected by 

 a less conspicuous fibrous substance ; and from the micro- 

 somes of the inner circle to the microsomes of the outer cir- 

 cle radial fibers connecting these can be observed (PI. XIV, 

 Figs. 45-47). The minuteness of the inner circle and the 

 body contained in it does not permit a determination, at this 

 stage, of the presence or absence of radial fibers surrounding 

 the central granule. The central granule, however, is present, 

 though its minuteness often renders its detection difficult. 



I do not hesitate to say that this is the centrosome of the 

 dividing oogonia, and that the central granule, with its sur- 

 rounding structure, corresponds very closely to that described 

 by van Beneden in the dividing egg of Ascaris. 



The centrosome and surrounding circles of microsomes, 

 with their radial fibers, appear to be imbedded in a specially 

 modified, more or less amorphous substance which, through 

 the various effects of reagents and stains, renders the former 

 obscure or even invisible. For the present I will adopt the 

 term used by Boveri and call this imbedding substance archo- 

 plasm. This archoplasm is more conspicuous in some stains 

 than in others ; and for that reason the centrosome and sur- 

 rounding structure may alone be distinctly visible ; while with 

 other stains the archoplasm appears prominent, often showing 

 no internal structure. The former is true of such stains as 

 picro-carmine (Fig. 47) ; the latter is often true of such stains as 

 Lyon's blue and erythrosin and cyanin (Figs. 39, 40). A care- 

 ful comparison of these different effects shows that at other 

 stages both the radial system and circles of microsomes, as 

 well as the archoplasm, are present. 



Being a direct continuation of the centrosome of the divid- 

 ing oogonia, it cannot be said to originate in the cytoplasm of 

 the growing egg. 



