EFFECTS OF INJURY UPON SPERM. 243 



a cell was found in the late prophase of second cleavage, though 

 without a first cleavage plane. In this case the nuclei have been 

 able to divide again though the cytoplasmic division was never 

 completed. In most cases the cells which fail to finish the first 

 cleavage never go any farther. 



(b 2) A very few eggs were found in each of the experiments 

 which exhibited the above described attempted cleavage, in 

 which multipolar spindles were found. Unfortunately my pre- 

 served material contains very few of these eggs and the sections 

 of some of them were lost or badly broken in the process of 

 preparation. 



There are two different kinds of eggs which show this condition. 

 One kind has formed two polar bodies. There are very few of 

 these eggs which are in a condition good enough to work upon. 

 Although the cultures from which the eggs were taken were more 

 than 75 per cent, unfertilized these eggs seem to show evidences 

 of polyspermy. This is borne out by the fact that, in a few cases, 

 two sperm cells were seen to be attached to a single living egg in 

 cultures similar to those from which these eggs were taken. 

 Although it is conceivable that multipolar figures might arise 

 from causes other than polyspermy, it is very unlikely. I regard 

 the few observations of polyspermy in the living cultures as good 

 evidence that the few cases under consideration are due to the 

 entrance of more than one sperm cell. The observations men- 

 tioned under (a 2) above also point in this direction. 



(b 3) The other kind of multipolar figures is found in eggs which 

 show defective maturation. In one case an egg was found in 

 which the first polar body had formed. Just beneath it lay 14 

 chromosomal vesicles and in the center of the section about 20 

 vesicles lay near a strong cytoplasmic radiation. The presence 

 of the radiation probably indicates that a sperm nucleus has 

 fused with the egg nucleus, although the number of vesicles 

 which can be made out is below the diploid. Another sperm cell 

 lies in contact with the vitelline membrane, probably attached 

 to it. Although this is not a case of multipolar mitosis in itself 

 it is possible that the 14 vesicles near the animal pole, which 

 represent the second polar body, may enter into the cleavage 

 process and aid in the production of multipolar figures. One or 



