270 



N. YATSU. 



Fig. il. Egg cut vertically at the two-cell stage (10.30 A.M.) ; enucleated fragment on the left. 

 Fig. 12. The same at 2 43 P.M. Fig. 13. Egg cut at the four-cell stage (11.30 A.M.) ; enucleat- 

 ed fragment on the left. Fig. 14. The same drawn at 1.22 P.M. (the egg proper) and at 1.25 

 P.M. (enucleated fragment). All the drawing X igo. 



striction in the middle (Fig. 12). It, however, did not divide in two. 



Case F. An egg was cut at the four-cell stage by a vertical cut 

 parallel to one of the two cleavage planes (Fig. 13). The egg proper 

 divided normally showing that the centrosomes had not been cut off by 

 the operation. No asters appeared in the enucleated fragment. A deep 

 constriction was found around the enucleated blastomere as in Fig. 12. 

 It finally cut the fragment completely to four spheres, two large and two 

 smaller (Fig. 14). 



From the above five cases it will be concluded that a mass of 

 cytoplasm deprived of both the nucleus and aster shows various degrees 

 of division activity which is usually indicated by a constriction but some- 

 times is carried on to such a degree as the complete division eusues. 



2. Fixity of the Cleavage Planes. 



It should here be noted, as will be described in full elsewhere, that 

 when a portion of an egg is cut off at or prior to, the metaphase the result- 



