352 BOTANICAL GAZETTE [may 
about vigorously and revolving on their axes. Sometimes no locomotion 
was observed, the entire mass of sperms appearing to remain at the 
receptive spot, but often some of the sperms were observed to change 
their places and occasionally to leave the venter. In one case five 
sperms of Athyrium Filix-joemina were observed within an arche- 
gonium of the same species. All of these swam about within the 
venter and were observed to leave and reenter the venter several 
times. This prothallus when replanted on soil gave no embryo; 
the egg, therefore, was probably bad. In every case when sperms 
were observed within the venter and fusion resulted, the mass of 
sperms was observed to remain in contact with the egg. Perhaps a 
good egg attracts the sperms, while a bad egg does not. 
Since in the cases mentioned the sperms were observed to bore 
against the receptive spot of the egg of another species as vigorously 
as they bored against the egg of their own species, it seems that the 
failure of such sperms to penetrate the egg is not due to any failure 
of the sperm to perform its part in the process. The failure of such 
sperms to enter the egg seems to be due either to some hindrance on 
the part of the egg or to some interaction of egg and sperm. There 
is little evidence to help us to decide between these two possibilities. 
VoEGLER observed that, after the entrance of one sperm, a second 
sperm, although boring against the egg, was unable to enter. This 
would appear to be due to some change occurring within the egg, Pe 
haps comparable to the formation of a membrane in the fertilized 
animal egg. 
FARMER (13) suggests that the entrance of more than one sperm 
into the egg is prevented by the occurrence of chemical changes in 
the cytoplasm of the egg immediately upon fertilization. He believes 
that these chemical changes produce substances which are injurious 
to the sperms, and presents some evidence for such an occurrence 
in the alga Halidrys. The entrance of a second sperm is not, however, 
always prevented. Morrtrer (34) has figured two sperms within 
one egg of Onoclea Struthiopteris, and WoopBURN (52) has described 
two remarkable cases of polyspermy in the same species; in one 0 
these, seven sperms were observed within the egg nucleus. Whether 
similar phenomena may occur in other species is not known. 
Morean (32, 33) has shown that in the ascidian Ciona, the sperms 
