No. 6.] INDIVIDUALITY OF THE GERM NUCLEI. 259 



In Crepidula plana I have observed a separateness of the 

 germ nuclei in certain stages of the nuclear cycle which is of 

 such a character that it may lead to the discovery of similar 

 phenomena in other animals. This separateness is most easily 



ON 



FIGS. 7 and 8. Anapliase and Telophase of Second Cleavage. Fig. 7, an abnormal egg in 

 which the left half has divided normally and the chromosomal vesicles of the daughter-nuclei 

 are fusing; in the right half the division figure is double with four spheres and two groups of 

 chromosomal vesicles which have not fused; there are thirty chromosomal vesicles in each 

 group. Fig. S, a normal egg showing the egg and sperm constituents in each of the 

 daughter-nuclei. 



FIG. g. Telophase of Second Cleavage ; centrosomes, spheres, and nuclei rotating in direction 



of arrows. 

 FIG. 10. Anaphase of Third Cleavage. Egg and sperm constituents of nuclei indicated. 



observed in the telophase of each division, though in some 

 cleavage cells it may be seen in the prophase also, or even 

 throughout the resting period. At the time when the daughter- 

 nuclei are being formed the chromosomal vesicles fuse into two 



