1 62 T. H. Morgan. 



These, and some other experiments that need not be described 

 here, show that salt-solutions of various kinds have a marked 

 effect in arousing to activity the inactive spermatozoa of the vasa 

 deferentia. They also make active, spermatozoa that are quies- 

 cent in distilled water. On the other hand ether, alcohol, and 

 ammonia, which proved so efficient for the spermatozoa of the sea- 

 urchin and starfish, appear to have little effect on the spermatozoa 

 of the mouse. 



The more fundamental physiological question as to the nature 

 of the action of these different substances I shall not attempt to 

 discuss without a further basis of observation and experiment to 

 go upon. Enough has been seen, however, to suggest that the 

 substances act as a "stimulus," which is perhaps not dissimilar in 

 kind from that which causes some eggs to begin to develop, or 

 a nerve impulse to start, or a muscle to contract. Here also we 

 may urge, as I have urged elsewhere^ in opposition to Loeb's 

 conclusion in regard to the action of certain agents in causing 

 artificial parthenogenesis, that the nature of the stimulus is of 

 such a kind that the result depends much more on the structure 

 or the composition of the living thing than upon the kind of 

 stimulus employed. So unstable is the living organization that 

 the sHghtest change brought about in it by chemical or by physical 

 means suffices to set into action a perfectly definite and pre- 

 arranged series of events. 



HISTORICAL REVIEW. 



The action of ether, ammonia and alcohol on the speramtozoa 

 of Ciona, arousing them to greater activity and thus, under certain 

 conditions, bringing about the fertilization of the egg, raises the 

 question as to whether in the higher animals a similar action may 

 not result from the application of these and of other substances, 

 and also whether the secretions of some of the glands connected 

 with the reproductive system may not have a similar effect on the 

 spermatozoa. 



When I tried to find some substances that might bring about 

 self-fertilization in Ciona I was not aware that there had already 



1 Science. N. S. XI. 1900. Pp. 178-180. 



