29S JORDAN. [Vol. VIII. 



as a "knot" is not particularly descriptive, as a glance at my 

 figures will suffice to show. 



At the time when the egg reaches nearly its full size, when 

 the yolk is formed and the yolk-nuclei have attained their maxi- 

 mum complexity, when the nucleoli are largest and most numer- 

 ous, there begins that remarkable centripetal march of the 

 nucleoli which foreshadows their speedy disintegration. The first 

 sign of this retrogressive movement is the peculiar appearance 

 of the nucleoli while still at the periphery. They stain feebly 

 and very unevenly, their outlines display the greatest roughness 

 and irregularity and they are plainly in every respect experi- 

 encing degenerative change (see Fig. 16, PI. XVI). The cen- 

 tripetal movement is not simultaneous on the part of all nucleoli. 

 Some are to be found at the periphery while others are in the 

 last stages of dissolution in the center. They usually straggle 

 severally to the center and there fall apart, as shown in Fig. 1 5, 

 PI. XVI, where several nucleoli are seen disintegrating en 

 route. Subsequent stages are well shown by Schultze ('87) in 

 Figs. 20 and 23. 



I must strongly dissent from certain of Schultze's conclusions 

 as to the fate of the nucleolar substance. After describing the 

 disintegration of the nucleoli into small granules he adds : 

 "Man iiberzeugt sich, dass die Kornchen, die ich jetzt Mikro- 

 somen nennen darf, allmahlich zur Erzeugung eines Faden- 

 knduels zusammentreten, der also nicht aus einem prdformirten 

 Kerngeriist entsteht, soiidern sich direkt aiis den winzigcn Kcim- 

 korperchen herausbildet." (p. 198.) I cannot agree with Schultze 

 that the granules from the disintegrating nucleoli go to build 

 up the " Fadenknauel." The granules resulting from the 

 nucleolar dissolution are simply strewn throughout the central 

 part of the vesicle (Fig. 1 5), and to the best of my observation 

 ultimately mix with the rest of the Qgg substance at the time 

 of the dissipation of the germinal vesicle. There is indeed no 

 preformed "nuclear network," but since there never is a very 

 clear network in the amphibian Qgg this is beside the question. 

 There are, however, chromatin threads or chromosomes distinctly 

 traceable tJirongh the whole history of the germinal vesicle. 

 These preformed chromosomes seem to have been overlooked 



