ACTION OF THE SPERMATOZOON UPON THE Eaa 237 
and that the second treatment with the hypertonic solution 
might only be needed to create a centrosome de novo in the 
egg. The idea was not probable, since we saw that the mem- 
brane formation alone suffices to provide the egg with the centro- 
somes and astrospheres necessary for cell division, as the egg 
is able to segment. if the temperature is not too high; and sec- 
ond that it is possible to substitute for the hypertonic solution 
the suppression of oxidations, a factor which directly sup- 
presses the production of astrospheres. Moreover, the experi- 
ments by Hindle have shown that the centrosomes are not 
formed while the eggs are in the hypertonic sea-water. The 
following observations and experiments by the writer indicate 
that the hypertonic solution does not act in these experiments 
by the creation of astrospheres or centrosomes. 
When we’ put the unfertilized eggs of S. purpuratus directly 
into hypertonic sea-water (without submitting them to the 
butyric-acid treatment) and if we put them back at different 
intervals into normal sea-water, we find that if the eggs have 
been exposed a sufficiently long time (two hours or more) to 
the hypertonic sea-water a number will begin to segment. 
These eggs will often go only into the two- or four-cell stage, 
or sometimes to the eight- or sixteen-cell stage, and then stop 
developing. They cease to divide, and remain in the resting 
stage.! Such eggs remain after this perfectly normal and they 
have the appearance of small unfertilized eggs. If we wait 
for some time, say twenty-four hours, to make sure that they 
neither develop nor disintegrate, and add sperm, each one of 
these blastomeres forms a tightly fitting membrane. They 
begin to develop in a perfectly normal way and into normal 
larvae. We are then dealing with eggs which, after having 
been treated with hypertonic sea-water, were in possession of 
the whole apparatus for cell division, since they actually had 
1 This phenomenon is much more common in the eggs of S. purpuratus than 
in those of Arbacia. 
