106 CHARLES PACKARD 



atin. The vesicles, which have not developed into the spireme 

 stage, are scattered irregularly about in the protoplasm. The 

 large number of vesicles, with forty-two karyomeres, and two 

 asters, indicates that two sperm nuclei are present. But they have 

 ceased to develop and their astral systems have failed to develop 

 normally. This failure is evidently not due to polyspermy for 

 polyspermic eggs develop in a different and characteristic manner. 

 To sum up: The effect of radium on the unfertilized eggs is 

 seen after fertilization with normal sperm in both the protoplasm 

 and the chromatin. The failure of the surface layer to be given 

 off is due to a change in its constituents under the influence of 

 radium. This failure leads to abnormalities in the formation of 

 the polar bodies. The chromatin at first displays very little 

 evidence of injury. Later, however, the injury shows in the fail- 

 ure of the egg nucleus to develop properly. The sperm nucleus 

 also fails to develop in these cases. 



d. The development of embryos 'from radiated eggs fertilized 

 by normal sperm 



The later development of these eggs is not different from that 

 of the normal eggs fertilized by radiated sperm, but the propor- 

 tion of unfertilized eggs is greater, and the rate of development-is 

 slower. This may be inferred from the fact that the sperm, in 

 many cases, cannot enter the egg for more than an hour after 

 insemination because the cortical layer is still present. Occa- 

 sionally some eggs divide into three or four parts at once, or, if 

 into two blastomeres, the relative sizes of the two are abnormal. 

 The subsequent development is also greatly retarded. When 

 the control embryos are already in the early trochophore stage, 

 these have not yet acquired the protrochal ring of cilia. A large 

 proportion die before they reach the trochophore stage. Whether 

 the proportion of abnormalities is greater in this series then in the 

 first is hard to say, since always in the controls, a few embryos are 

 abnormal. The type of abnormality that develops is precisely 

 the same as that described in the preceding section. 



