EFFECTS OF RAYS OF RADIUM ON PROTOPLASM 337 



the chromosomes, following the extrusion of the second polar 

 body, develop into large chromosomal vesicles. Such an egg is 

 shown in figure 10. The sperm is seen still exterior to the egg 

 membrane which is not lifted far off from the egg. There are 

 at least 40 vesicles present in the entire egg and the karyomeres 

 number about 250. Such a number of vesicles is probably due 

 to more than one division of the chromosomes at the first meta- 

 phase. The karyomeres may have fragmented by direct division. 

 Subsequently they have grown, since each one is fully as large 

 as those found in normal eggs. 



The third type of development is seen in eggs radiated with 

 the rapid beta rays at 4 mm. distance. The increase in the 

 width of the perivitelline space is much more marked than in the 

 preceding type, for it appears earlier and is greater in extent. 

 More than 75 per cent of the eggs show such an abnormality. 

 In the great majority of cases the sperm does not enter at all, 

 and can be found more than an hour after insemination still 

 outside of the egg. This phenomenon may be due to the fact 

 that the vitelline membrane is so rapidly pushed away from the 

 egg that no fertilization cone could extend far enough out from 

 the egg to reach it (fig. 11). 



The development of these eggs proceeds normally until the 

 time when the sperm should enter, that is, through the first 

 metaphase. The chromosomes are not extruded, and no first 

 polar body forms at all. The inner centrosome of the spindle 

 divides forming well marked tripolar and multipolar spindles 

 (figs. 11 and 12). Figure 13 shows a small protoplasmic pro- 

 tuberance at the point where the polar body should be given off. 

 This is a very common^ phenomenon. The chromosomes which 

 are very numerous, owing to the multipolar divisions, now 

 become vesicular, just as they do in normal eggs at the end 

 of the second polar division. In the meantime the second polar 

 body has been extruded although the method, as in the preceding 

 case, is obscure. I could not determine how many chromosomes 

 are extruded at this time, but from indirect evidence I believe 

 the number to be 14, that is, the haploid number. The remaining 

 chromosomes, of which there may be 28 or 42 or even more, 



