MEMBRANE FORMATION IN FERTILIZATION. 9 1 



to the rapid death of the latter, if it is kept at room temperature 

 and if it does not receive a second treatment either with a hyper- 

 tonic solution or lack of oxygen. This case was fully discussed 

 by the writer in a recent paper.^ It is therefore not justifiable 

 to conclude that the action of butyric acid on the unfertilized 

 egg must be identical with the action of the same substance on a 

 fertilized egg, treated beforehand with the sperm of Sahellaria. 



Should it be possible that Brachet's "couche corticale" is the 

 chorion or the "jelly" which surrounds the unfertilized egg? 

 But this jelly is normally dissolved when the egg is fertilized. It 

 might be conceivable that the sperm of Sahellaria causes a harden- 

 ing and a contraction of this jelly which protects it against being 

 dissolved by the sperm of the sea urchin and that subsequent 

 shaking or a subsequent treatment with acid destroys this jelly. 

 But granted this were the case, it would be erroneous to use 

 experiments on an artificially altered chorion to draw conclusions 

 upon the r61e of membrane formation in fertilization or artificial 

 parthenogenesis . 



The writer wonders how Brachet (or Herlant) are going to 

 harmonize the following well-established facts with their views. 

 If the eggs of Strongylocentrotus purpuratus are treated with 

 hypertonic sea water for about two hours, they form in most 

 cases no membrane and nothing happens to them except that a 

 certain percentage of them begin to divide very regularly into 

 2, 4, 8, possibly 12 or 16 cells and then stop. Such eggs are to 

 all appearances in the resting stage and live as long as the other 

 unfertilized eggs if nothing is done to them. If they are fertil- 

 ized by sperm each blastomere forms a special fertilization mem- 

 brane and now each blastomere develops into a blastula or into 

 a pluteus, according to the size of the blastomere. They also 

 develop into plutei if an artificial membrane formation is called 

 forth with the aid of butyric acid. The writer is inclined to 

 explain this phenomenon by assuming that the treatment with 

 the hypertonic solution called forth two effects, one of which 

 was a peripheral change resulting in an increase in the rate of 

 oxidations. This effect is, as the writer has shown, reversible 



1 Loeb, "Weitere Beitrage zur Theorie der kiinstlichen Parthenogenese," Arch, 

 f. Entwcklngsmech., XXXVIII. , 409, 1914. 



