Artificial Parthenogenesis in Thalassema Mellita 135 



were faintly visible to fall into three or four cells, respectively, at 

 the first cleavage. Cytoplasmic division, however, does not by 

 any means always follow a multipolar mitosis which may occur 

 repeatedly in one and the same cell. That this is true is clearly 

 proven by the large number of chromosomes often present in such 

 cells. Fig. 58 shows an abnormal embryo in which one cell has 

 evidently failed to undergo cytoplasmic cleavage and in which a 

 multipolar mitosis is taking place. A similar condition is seen in 

 Fig. 55 which presents a maze of spindles and asters in the unseg- 

 mented egg. 



Cytasters in the acid treated eggs of Thalassema are of rare 

 occurrence, and only occasionally does one find an aster which is 

 not associated with nuclear material. In fact, I have never been 

 able to thoroughly satisfy myself that I have observed a true 

 cytaster, but in cases like Fig. 55, the small asters lying near the 

 periphery of the egg, some of which show a central granule, 

 may possibly be of this nature. 



At the close of a multipolar mitosis, the numerous chromosomes 

 are either gathered into a single large nucleus, which is usually 

 polymorphic in character (Fig. 56), or apparently many separate 

 smaller nuclei may be formed which increase in size during the 

 resting period (Fig. 57). Frequently the latter are lobed or con- 

 stricted, as if dividing amitotically (Fig. 57), and it is also probable 

 that they fuse at times into a single large nuclear area. I am 

 inclined to believe that such eggs rarely segment, as they are 

 especially numerous in dishes in which the developing eggs have 

 reached late blastula and gastrula stages. 



b Giant Bipolar Figures 



In more or less abnormal embryos, I have quite often found 

 large cells, in which segmentation had evidently not kept pace 

 with nuclear division, that were characterized by the presence of 

 a single giant spindle bearing an enormous number of chromo- 

 somes. Fig. 59 illustrates a case in point. In the cell marked a, the 

 spindle is abnormally large, while the equatorial plate is densely 

 packed with small chromosomes which are greatly in excess of the 

 usual number. In cell b of the same figure, a similar spindle, but 



