STUDIES OF FERTILIZATION 437 
observations of polyspermy in none of which was implantation 
nearly close enough together to produce a single cone; in one series 
that I possess many eggs have thirty or more spermatozoa im- 
planted, but the points of insertion are always separate. More- 
over, in such a case one would expect the cone to be larger than 
usual, but in this case it is a little below the average size; one 
would also expect to find two equal groups of implantation 
granules with separate attachments of the nuclei, but only one 
group and one attachment is found here, viz., in the nucleus to the 
left; the granule near the right nucleus is too small to represent a 
separate implantation group, and moreover, it has no connection 
with the neighboring nucleus. Finally, it will be seen that con- 
ditions such as those illustrated in figs. 27 and 28 must inevitably 
lead to the condition of fig. 40 if the fragments of the sperm head 
do not reunite. 
There is thus every reason for interpreting these two nuclei 
as parts of a single one. This rare find smply emphasizes the 
conclusions already reached concerning the fertilizing power of 
portions of the sperm head. 
Without attempting at this place to discuss the results fully, I 
would, nevertheless, emphasize the two facts of greatest impor- 
tance already brought out. In the first place it is shown that an 
apical fragment of the sperm head is able to produce an accompany- 
ing aster in the egg cytoplasm; the sperm aster has therefore no 
necessary relation to the middle piece of the spermatozoén, or to the 
centrosome of the spermatid. In other words, using the formation 
of a sperm aster as criterion, the fertilizing power of the spermato- 
zoon is not localized in the middle piece, as supposed by Boveri 
and others, but is a function of even small fragments of the sperm 
nuc’eus alone. In the second place the great beauty of this 
material is that the orientation of the sperm nucleus, whether 
entire or partial, is preserved until after the origin of the sperm 
aster, and this enables one to determine that the sperm aster 
always arises in relation to the most basal point of the sperm 
nucleus. Altogether, I have observed well over one hundred 
cases of entire and partial sperm nuclei in these stages, and have 
never found any exception to the rule that the sperm aster arises 
