90 JACQUES LOEB. 



corticale" the larvae can hatch and are now able to develop into 

 plutei. The only membrane, however, which can prevent the 

 eggs from hatching is the fertilization membrane, and it is im- 

 possible to harmonize the two statements of Brachet, first, that 

 these eggs have no fertilization membrane and, second, that the 

 gastrulae cannot hatch unless the membrane of the egg is pierced. 

 Professor Goldschmidt, to whom I showed Brachet's paper sug- 

 gested that Brachet probably means by "couche corticale" the 

 hyaline membrane (Herbst's "Verbindungsmembran") which 

 surrounds the blastomeres and that he assumes erroneously that 

 this hyaline membrane forms a continuous layer around the 

 blastula in the same way as the fertilization membrane does. 

 This is, however, not the case since the hyaline membrane par- 

 ticipates in the process of segmentation and forms a distinct layer 

 around each individual blastomere, but not a continuous envelope 

 around the whole blastula. 



Brachet's observation is intelligible on the assumption that the 

 egg after it has been treated with the sperm of Sahellaria forms 

 a very tightly fitting membrane when it is fertilized with its own 

 sperm and that this membrane must be torn by shaking the 

 egg in order to allow the blastula to hatch (or to escape from 

 being killed by the mechanical pressure of the tightly fitting 

 membrane?). Brachet found also that it is possible to sub- 

 stitute for the shaking of the egg a treatment with butyric acid, 

 which as he assumes also tends to remove the obstacle to the 

 hatching. This may be correct, but unfortunately he draws 

 the further conclusion that the butyric acid treatment must have 

 the same effect upon the unfertilized egg as upon the fertilized 

 egg which has previously been treated with the sperm of Sahel- 

 laria. Leaving aside the fact that the unfertilized egg has no 

 membrane, it has been shown that the butyric acid treatment 

 raises the rate of oxidations of the unfertilized egg about 400 or 

 600 per cent., while acid does not increase, but, on the contrary, 

 lowers the rate of oxidations in the fertilized egg. Moreover, the 

 writer has shown that if a fertilized egg is treated with butyric 

 acid, in the same way as is required for inducing artificial parthe- 

 nogenesis, the fertilized egg is not injured, while the inducing of a 

 membrane formation by butyric acid in the unfertilized egg leads 



