EFFECT OF RADIUM ON FERTILIZATION 105 



After the maturation period the remaining chromatin collects 

 in one or more large vesicles of normal appearance. Occasionally 

 the number of such vesicles may be very large and the karyomeres 

 very numerous. The extra number may be due to the fact that 

 the polar bodies have not been extruded, so that there is much 

 extra chromatin. The subsequent behavior of these vesicles 

 differs accordingly to whether they fuse with the sperm nucleus or 

 not. In the former case the fusion may be entirely normal, 

 and the subsequent division perfectly regular. Or the cleavage 

 nucleus may never divide, but, on the contrary, increase consider- 

 ably in size until it is nearly half as large as the germinal vesicle. 

 The chromatin, in the meantime, breaks up into minute granules 

 and passes out from the nucleus into the surrounding protoplasm. 

 Figure 20 shows such an instance. The nuclear wall displays no 

 breaks through which the granules might have passed out bodily. 



Such a condition might be explained on the basis that the egg 

 chromatin had been injured by the radiations and had formed, as 

 a result, a poison, which affects the sperm chromatin. The general 

 effect of the radiation is to cause the chropiatin to break up 

 into granules. This is the explanation suggested by G. Hertwig. 



If the sperm nucleus does not fuse with the egg nucleus it fails 

 to develop past the spireme stage, and in many cases does not 

 develop even as far as that. Up to this time it has behaved 

 normally. Even when many sperms enter (fig. 19) each one 

 pursues the normal course in the egg. In figure 21 are shown two 

 sperm nuclei in several separate vesicles, in which the karyomeres 

 have fused and commenced to draw out into spiremes. Which 

 vesicles belong to the egg and which to the sperm nuclei is diffi- 

 cult to determine since they have become exactly the same in ap- 

 pearance. In such a case, if a poison has been generated, it has 

 failed to produce any marked effect on the egg chromatin itself. 

 The only apparent abnormality is the failure of the nuclei to fuse. 



Division of the egg may occur without the appearance of 

 asters and without division of the chromatin. Figure 22 shows an 

 egg in which all the chromatin is in one blastomere. Figure 23 

 shows the protoplasm dividing without any division of the chrom- 



