296 JORDAN. [Vol. VIII. 



expect truer pictures of nuclear structure with the use of the 

 latter reagents than with the former, but one cannot com- 

 pletely exclude the possibility that, as regards this particular 

 character of the nucleus, the picro-sulphuric mixture preserves 

 the natural aspects better than the other killing fluids named, 

 I do not, however, believe that such is the case, and I consider 

 the reticular appearance as probably due to the action of the 

 reagent. 



With regard to the accumulation of fluid around the germinal 

 vesicle in advanced stages I agree fully with v. Bambeke, 

 Hertwig and Schultze, that it is not a natural condition, but is 

 caused by osmotic action during the processes of killing and 

 hardening. When the Qgg is hardened slowly in rising grades 

 of alcohol this escape of fluid does not occur, and the germinal 

 vesicle impinges directly upon the yolk. (Figs. 15, 16, 17). 



Nucleoli. — The nucleoli in the young Q^g appear arranged 

 along the chromatin threads, and possibly originate from the 

 thread substance. It is very difficult to determine just what 

 relation the nucleoli bear to the threads in the earliest stages. 

 The fact that the two structures are in the closest contact 

 does not exclude the possibility of distinct and independent 

 origin. The nucleoli are at first, to all appearances, integral 

 parts of the threads, at least as much so as the highly refractive 

 granules of the threads shown in Fig. 14, PL XV. I must leave 

 it an open question just how far it is safe to regard the early 

 association of nucleoli and threads as indicating a common 



*t> 



origm. 



In eggs somewhat younger than Fig. 4 the nucleoli exist in 

 this intimate association with the threads, but they soon lose 

 their connection, increase rapidly in number and size, and come 

 to lie close to the periphery of the vesicle. O. Schultze ('87) 

 reffards the increase in the number of nucleoli as due to division 

 of those first formed, but he does not raise the important ques- 

 tion as to how the first nucleoli originate. My own observations 

 have led me to conclude that the nucleoli never multiply by 

 division. I have repeatedly sought in vain, both in fresh eggs 

 and in sections, for nucleoli in the act of fission. Schultze 

 states, in support of his view (p. 195), that the nucleoli in very 



