418 BOTANICAL GAZETTE [DECEMBER 
probably, with some gas. In this way there is formed at the apex 
of the egg a vacuole, which may be of very short duration. In 
the absence of more definite knowledge, we suggest that this series 
of conditions would result in drawing the sperm into the egg, the 
cilia merely keeping it oriented, for sperms just within the egg 
showed the apex in advance in every case observed. It has already 
been noted in the paper on spermatogenesis (8) that the sperms 
have an amoeboid movement in addition to the movement by cilia. 
This amoeboid movement doubtless facilitates the entrance into 
the egg. 
While the whole sperm enters the egg, the nucleus soon slips 
out from the cytoplasmic sheath and moves toward the egg nucleus, 
leaving the sheath with its ciliated band in the upper part of 
the egg. It may be that the constriction of the sperm during its 
entrance into the egg loosens the sheath from the nucleus so that 
it slips out more readily, for projections of various sizes extend 
from the nucleus into the sheath, and these would naturally become 
loosened. When more than one sperm enters the egg, it is worth 
noting that the nucleus of the second sperm does not slip out from 
the sheath, but remains intact in the cytoplasm at the top of the 
egg, where it may be distinguished to rather late stages in the 
development of the proembryo. Doubtless the first sperm opened 
the neck of the archegonium, so that the second suffered little 
constriction and the cytoplasmic sheath was not loosened. In 
some cases, at least, the sperm is still capable of vigorous movement 
after it is within the egg, as may be seen in fig. 1, where the contents 
of the egg have been stirred by the vibration of the cilia. 
The cytoplasm of the sperm gradually mingles with that of the 
egg, and the two soon become indistinguishable, but the ciliated 
band maintains its identity much longer, and may be distinguished 
throughout the free nuclear development of the embryo, after which 
it becomes faint and finally merges with the cytoplasm of the upper 
part of the egg. As in Zamia (4), portions of the band occasionally 
penetrate farther, sometimes being found below the middle of 
the egg. The cytoplasm never surrounds the fusion nucleus, as 
in some gymnosperms, and there is no indication that it exerts any 
active influence upon the egg. That it does not stimulate 15 
