ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 687 
Strongylocentrotus are able to develop into plutei in normal 
sea-water, I can say that this is most certainly not the case 
at Woods Hole, in California (according to my own very 
numerous observations), in Beaufort, N. C., and at Naples 
and other places on the Mediterranean, that have been 
visited by competent experimenters. 
X. THE BEARING OF ARTIFICIAL PARTHENOGENESIS ON THE 
THEORY OF FERTILIZATION AND OF LIFE PHENOMENA IN 
GENERAL 
The general opinion concerning the role of the sper- 
matozoon in the process of fertilization is that it acts as a 
stimulus, and that as such it starts the development of the 
egg. This statement is certainly wrong for those eggs in 
which we have been able to produce artificial partheno- 
genesis. For these eggs, like many others, begin to segment 
without any spermatozoon, if they are left long enoughin normal 
sea-water. The only difference between these and the fertil- 
ized eggs)is that the former begin to segment much later and 
their development stops in the early segmentation stages (two 
to sixteen cells at the most). The latter may be due to the 
fact that the egg dies before it has time to develop further. 
If we consider the fact that the eggs show at least a be- 
ginning of a segmentation under ‘“‘normal” conditions, the 
act of fertilization assumes a different aspect. The sper- 
matozoon can no longer be considered the cause or the stimu- 
lus for the process of development, but merely an agency 
which accelerates a process that is able to start without i, 
only much more slowly. Substances that accelerate chemical 
or physical processes which would occur without them are 
called catalyzers (Ostwald). According to this definition we 
may assume that the spermatozoon carries a catalytic sub- 
stance into the egg, which accelerates the process that would 
start anyhow, but much more slowly. 
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