ROBERT CHAMBERS 



67 



Wilson,' in producing binucleate eggs by artificially obliterating 

 the first cleavage furrow, noted that when this was caused by shaking, 

 the resulting binucleate eggs retain the elongated shape (Fig. 13) 

 characteristic of the egg in cleavage. During the ensuing pause 

 (corresponding to the completion of the first cleavage and when 



Fig. 13. Copy of Fig. 58 from Wilson'^ of Toxopneusles ovum immediately after 

 shaking which caused obliteration of the first cleavage furrow. 



Fig. 14. Copy of Fig. 34 from Wilson' of Toxopneusles ovum in which obliter- 

 ation of the first cleavage furrow was produced by exposure to ether. 



the astral radiations fade out preparatory to formation of a new 

 amphiaster system) the egg becomes more nearly spherical. Evidently 

 the shaking does not necessarily produce a reversal of the semisolid 

 astral system to the more fluid state. As soon, however, as this 

 occurs (in the ensuing pause) the egg resumes its spherical shape. 



