lyo T. H. Morgan. 



tozoon from the egg of the same individual was due to the size 

 of the pores, because there would be eggs of some other individuals 

 having pores as small or smaller. Another possibility that sug- 

 gests itself is that the surface tension of the egg is of such a sort 

 that it excludes the spermatozoa of the same individual, but this 

 idea does not appear to give a satisfactory solution, for, aside 

 from the fact that it is difficult to imagine how such a relation 

 could exist, there would also occur cases in which the surface ten- 

 sion of the eggs of other individuals would exclude certain sperm, 

 and this does not appear to be the case. It is true that the ad- 

 dition of the ether to the water may cause a difference in the 

 surface tension of the egg, and it might be made to appear that 

 this was the way in which the self-fertilization is effected in the 

 ether-solutions, but I can not believe that this is the explanation 

 of the results, because other experiments show that a considerable 

 amount of ether is necessary to cause self-fertilization. 



It seemed to me that violent shaking might so affect the sur- 

 face of the egg that self-fertilization might take place. A 

 number of eggs from the oviduct were violently shaken for a 

 few minutes in a small vial, and then sperm from the same in- 

 dividual was added. No segmentation took place, and the pre- 

 sumption is therefore that the eggs were not fertilized. 



Turning to the chemical side we find a number of possibilities 

 that demand consideration. The inactivity of the immature sper- 

 matozoa, and the lack of power of such sperm to fertilize the egg, 

 their becoming active in certain solutions, and their power then 

 to fertilize eggs that they did not fertilize before, as best shown 

 in Cynthia, suggests that normally the eggs may secrete certain 

 substances that make more active the spermatozoa, which then be- 

 come capable of fertilizing the eggs. This view appears all the 

 more attractive in the present case on account of the observed leth- 

 argy of the spermatozoa of these ascidians, and the apparent con- 

 nection in such cases between this condition and the impotence of 

 such sperm in fertilization. Yet after careful consideration I am 

 not prepared to advocate this view as the only solution, although I 

 realize that it might be made to give the appearance of a ready 

 explanation of my results. Not that this induced activity may not 



