350 LOUIS I. DUBLIN. 



deeply staining, very much like the granule of a centrosome. It 

 is important to observe, that the number is at this point always 

 two, the one larger nucleolus occurring only in the later stages 

 of spermatogonial development. The chromatin soon increases 

 in staining power, the nuclear membrane stands out more clearly 

 and the two nucleoli increase in size until they become very con- 

 spicious. In the Auerbach preparations, the green chromatin 

 reticulum near the nuclear membrane stands out rather clearly 

 from the two red plastin nucleoli. These, at this point, 

 approach the center of the nucleus and finally fuse into one 

 larger nucleolus. All the stages in the approach of the two are 

 to be found in one microscopic field in almost any testis. The 

 appearance of these bodies as they come into closer relation, 

 indicates that there is a flowing of their liquid substance toward 

 a common center. In this way is produced a fine strand, deeply 

 staining, which connects them before they have fused. We can 

 now more readily understand the prevalence of the single nucleoli 

 in resting spermatogonia. They represent the two, which, origin- 

 ally distinct, have now fused. It must here be added, however, 

 that there is some doubt whether the two always fuse into 

 one. There is evidence for the possibility that, in some few 

 cases at least, the two remain distinct until the formation of the 

 next spindle figure when they disintegrate. 



The chromatin by this time stains much more intensely and 

 takes the form of definite chromosomes. These may now move 

 from the periphery and come into closer relation with the one or 

 the two nucleoli. This connection is, however, always a second- 

 ary one, and in no case represents the origin of chromosomes from 

 chromatin nucleoli. There can be little doubt of this conclu- 

 sion, for on staining with Auerbach's fluid the chromatin stains 

 intensely green while the nucleoli are always red. The same 

 decisive results were obtained with the use of the Borel stain. 



The oogonia at first resemble the spermatogonia very closely 

 (Fig. 3) but can be distinguished, even at an early period, by 

 their smaller number. The chromatin goes through exactly 

 the same transformation in the several generations as do also 

 the two nucleoli. In their early appearance at or near opposite 

 points on the newly formed nuclear membrane, in their subse- 



