176 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
is much more conspicuous in one of them (Fig. 21a) than in the other. 
A single well marked aster, without visible centrosome, sustains an 
interesting relation to the vesicles of the compound nucleus. It lies 
somewhat nearer the surface of the egg than the three more or less 
confluent vesicles, and the more pointed ends of these appear as though 
drawn out in the direction of the centre of the aster. ‘This aster is on 
the side of the vesicles which faces the other nucleus, in connection 
with which there is no aster or other cytoplasmic differentiation. In 
the absence of an entrance cone or of a cytoplasmic ‘track,’ which, 
as we have seen, are characteristic of some sperm nuclei, it is difficult 
to decide which is the sperm nucleus. In another egg the aster was 
found to accompany the sperm nucleus (Fig. 16a), but, on the other 
hand, the multi-vesiculate condition is more characteristic of the egg 
nucleus. ‘The compound nucleus, the one accompanied by an aster 
(Fig. 21b), has a shortest diameter of about 20 4, whereas the other 
nucleus is only 9 # in diameter; this seems to give evidence that the 
compound one is the egg nucleus. But even if this is so, the aster 
cannot be considered as belonging to the maturation spindle, since it 
is too prominent and not in the proper position, but must represent a 
new aster, which may perhaps persist to help form the cleavage spindle. 
The most extreme condition of distinct vesicles representing the 
germ nuclei, though not the only such case found, is shown in Figure 22. 
This Figure is compiled from two sections by a careful superposing 
of camera drawings, and shows all the nuclear bodies found in the egg. 
Three of the vesicles (a) lay wholly in one section, and within 10 y of 
the surface of the egg; the other vesicles (group b) were limited to the 
preceding section, and all were less than 20 » from the surface. All’ 
the vesicles were in a zone of more deeply staining cytoplasm, which 
extended to the surface of the egg, and no astral radiations were present 
in connection with any of the vesicles. Spermatozoa were present on 
the surface of the egg, and one had probably penetrated, since no 
attraction cone was present, and the surface of the egg showed the 
irregularities which we have seen to be characteristic of the time 
immediately following the penetration of a spermatozo6n. As neither 
sperm head nor other nuclear bodies were found in the egg, the vesicles 
figured must represent both sperm and egg nuclei. However, it is not 
possible to distinguish between the two. 
Polyspermy occurs frequently in Pennaria, and in such cases each 
sperm head is accompanied by a distinct aster, though the aster is 
usually lost when one of the sperms begins to metamorphose into a 
nucleus. Perhaps the presence of the aster in polyspermic eggs gives 
