68 PROTOPLASMIC CONSISTENCY AND CELL DIVISION 



Wilson noted that the suppression of the cleavage furrow can also 

 be produced by placing eggs, during their anaphase stage, in a 2.5 

 per cent ether solution. The astral radiations disappear and the 

 resulting binucleate egg at once resumes the shape of a sphere (Fig. 14) . 

 This phenomenon may be comparable to the experiments illustrated 

 in Figs. 6, 8, and 9 where the obliteration of the astral radiations 

 follows a precocious reversal of the cytoplasm to the more fluid state. 

 The suppression of the furrow in these cases seems to be primarily 

 effected by the change in the physical state of the egg substance 

 which, on reverting to a more fluid state, merges into a single spherical 

 mass. 



CONCLUSIONS. 



1. The development of the amphiaster is associated with the for- 

 mation of two semisolid masses within the more fluid egg substance. 



2. The elongation of the egg during cleavage is possibly produced 

 as a consequence of the mutual pressure of these two growing semi- 

 solid masses. 



3. The division of the egg into two blastomeres consists essentially 

 in a growth, within the egg, of two masses of material at the expense 

 of the surrounding cytoplasm. When all the cytoplasm of the egg 

 is incorporated in these two masses cleavage occurs. 



4. After a certain period of time the semisolid masses revert to a 

 more fluid state. In the eggs studied this normally occurs after the 

 cleavage furrow has completed the separation of the two blastomeres. 

 The formation of the furrow, however, may be prevented in various 

 ways, upon which the egg reverts to a single spherical semifluid mass 

 containing two nuclei. 



5. An egg mutilated during its semisolid state (amphiaster stage) 

 may or may not revert to a more fluid state. If the more soHd state 

 is maintained, the cleavage furrow persists and proceeds till cleavage 

 is completed. If the mutilation causes the egg to revert to the more 

 fluid state the furrow becomes obliterated and a new cleavage plane 

 is subsequently adopted. 



6. The nuclei of eggs in the semifluid state are able to alter their 

 positions. In semifluid mutilated eggs the nuclei tend to move to 

 positions which may assure symmetry in aster formation and cleavage. 



