98 CHARLES PACKARD 



exact picture of that found in eggs in which the radiated sperma- 

 tozoon has failed to enter. 



It is evident, then, that the radiation of the spermatozoa is 

 not responsible for the peculiar development of the egg nucleus. 

 Nor is the failure of the sperm to set up an appropriate reaction 

 in the egg which should ensure its entrance an efi'ect of the radi- 

 ations per se. For the same condition is occasionally found in 

 the controls. Probably any treatment which changes the sper- 

 matozoa would bring about the same result. 



To sum up the results of this experiment, it may be said that 

 the abnormal spermatozoa can be divided into two classes, ac- 

 cording to the reactions they initiate in the egg. Those of the 

 first class are able to activate the egg normally and are conse- 

 quently drawn into the egg protoplasm ; those of the second class 

 are able to produce this result only in part. The spermatozoa 

 of the first class induce the normal extrusion of the jelly, and the 

 formation of the fertilization cone, but they fail to develop the 

 normal cleavage asters and fail to fuse with the egg nucleus. The 

 second class of spermatozoa bring about the normal extrusion of 

 the jelly, and the formation of the fertilization cone, but cannot 

 stimulate the egg sufficiently to cause it to draw them in. This 

 defect results in the abnormal development of the egg nucleus. 

 It cannot be said that these spermatozoa are injured in the chrom- 

 atin alone unless it is held that any process that weakens their 

 vitality acts specifically on the chromatin. It is apparent, how- 

 ever, that the chromatin is actually injured. This experiment 

 shows that when failure of the nuclei to fuse occurs, the egg does 

 not develop at all, thus differing radically from the sea urchin egg 

 under similar conditions. 



b. The subsequent development of eggs fertilized by radiated 



sperm 



Cell division in the majority of eggs is normal, altjiough usu- 

 ally somewhat delayed. The chromosomes split in the normal 

 manner and form vesicles at the telophase. Later the vesicles 

 fuse to form the resting nucleus. No irregular mitoses were 



