130 



BERTRAM G. SMITH 



2. The dissolution of the germinal vesicle, and the formation of the 



first polar spindle 



Material for the study of this stage was obtained from two 

 females in which the majority of the ripening eggs had left the 

 ovary, and were found distributed in the body cavity, oviduct 

 and uterus. The nearly mature eggs left in these ovaries were 

 found in every case investigated (nine eggs were sectioned) to 

 have the germinal vesicle ruptured and its constituents well 

 mixed with those of the blastodisc; in the majority of cases the 

 first polar spindle had already formed. 



p.s. I 





' '"/^'M ...... s: 







Fig. 31 Meridional section through an ovarian egg of Cryptobranchus alle- 

 gheniensis, shortly after the rupture of the germinal vesicle. Fragments of the 

 germinal vesicle are seen scattered throughout the blastodisc. X 18. p. s. I, 

 first polar spindle. 



The rupture of the germinal vesicle and the distribution of its 

 materials throughout the blastodisc must take place with consider- 

 able rapidity, since in eggs sectioned only the beginning and the 

 end of the process have been observed. Fragments of the nuclear 

 membrane, together with the wavy fibrous material previously 

 noted in the germinal vesicle and innumerable fine granules, 

 probably derived from the cell sap, become widely scattered 

 throughout the germinal disc (see fig. 31). During this process of 

 disintegration of the germinal vesicle the nucleoli and chromatin 

 granules are lost to view. It seems improbable that all the chro- 

 matin granules should again be segregated as nuclear material; 

 at any rate the rupture of the germinal vesicle affords an oppor- 



