ARTIFICIAL PRODUCTION OF NORMAL LARV.E 617 



was always changed in both classes of eggs simultaneously, 

 and the chances for fertilization of the eggs from sperma- 

 tozoa contained in the sea- water were equal for both. If the 

 sea-water had contained any spermatozoa capable of impreg- 

 nating the eggs, those eggs that had been in solutions with 

 less MgCl 2 should have been fertilized first. 



4. In almost all the experiments eggs were taken out 

 of the mixture of 60 to 50 c.c. 2 n MgCl 3 +40 to 50 c.c. 

 sea-water at different periods. In no case did a single egg 

 develop into a blastula that had been in this solution for less 

 than one half-hour, and generally only those eggs yielded 

 blastulse that had been in this solution for about two hours. 

 If the sea-water had contained spermatozoa, the latter should 

 have fertilized those eggs first which had been a shorter time 

 in the artificial solution. On the other hand, the eggs that 

 had been left in the artificial solution more than two and 

 one-half hours as a rule yielded fewer or no blastulse. 



5. I stated above that even at the height of the spawning 

 season eggs are rarely fertilized by spermatozoa contained in 

 the running sea-water. I do not think one would be likely 

 to see more than one egg in a thousand undergo develop- 

 ment under such conditions, provided that no contamination 

 through the instruments occurred. In our experiments which 

 were made at the end of the spawning season about 20 to 50 

 per cent, of the eggs that had been kept in the right solution 

 developed. It is out of the question to attribute such a 

 result to spermatozoa contained in the sea- water. 



6. As far as I can see, there is only one possible source 

 of error left. It might be that the sea-water contained 

 spermatozoa, but that these spermatozoa were not able to 

 fertilize normal eggs, while a treatment of the egg with 

 the mixture of 60 c.c. 2 n MgCl 3 + 40 c.c. sea-water in- 

 creased its susceptibility to impregnation, or a treatment 

 of the spermatozoon with the same solution increased the 



