FERTILIZATION AFTER INITIATION OF DEVELOPMENT. 267 



20, 30 or 40 minutes, quite a goodly percentage of larval forms 

 are to be seen, but compared with the curve of larval production 

 of the hypertonic solution alone it has been increased very little 

 or not at all. We cannot, therefore, refer the swimming larva- 

 appearing in these inseminated cultures to fertilized eggs but 

 they can be regarded only as larvae that have developed from 

 the action of the hypertonic solution upon the eggs. Insemina- 

 tion did not increase the number of cleavages or swimming 

 larvae over that obtained after hypertonic activation alone. 



We can now consider more in detail the results of the experi- 

 ment under consideration and let it serve to illustrate the results 

 of most of the experiments. 



In an exposure to the weaker concentration of hypertonic 

 sea-water very few eggs give evidence of a cortical change that 

 in any way resembles the fertilization membrane produced 

 around the egg when normally fertilized, and in keeping with 

 this, very few of the eggs segment. It is difficult to say whether 

 or not every egg that cleaved had previously undergone a cortical 

 change. It is difficult even to say if an egg has cleaved or not, 

 for the cleavage patterns have been so variously modified, are 

 so irregular and these are scattered promiscuously among so 

 many eggs that are undergoing degeneration that it is very 

 difficult to determine whether an egg has segmented or is slowly 

 falling to pieces. Many times the cytoplasm of the egg pulls 

 apart, leaving a wedge-shaped opening that finally separates the 

 egg into two approximately equal halves with the nucleus con- 

 tained entirely within one half; and yet at other times nuclear 

 division may occur without cytoplasmic division. But that 

 there is not a membrane produced that will hold the blastomeres 

 together as in normal fertilization is very evident from the 

 fact that even the first two cells may fall apart and become 

 entirely separate from each other or be held together only within 

 the clear transparent jelly layer of the egg the chorion layer. 

 But a small percentage of the eggs do produce slight membrane 

 changes: the membrane appears around the egg and can be 

 easily seen with the higher powers of the microscope. They are 

 slightly thickened, clear jelly-like membranes adhering very 

 close to the egg and are not at all to be confused with a normal 



