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 r6le 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 enough in 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 it, 

 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. 



