FERTILIZATION ON PARTHENOGENESIS. 149 



Quoting from Loeb ('13, p. 234) : 



" If we call forth artificial membrane formation first by butyric 

 acid, no spermatozoon can enter the egg, since the fertilization 

 membrane is impermeable to a spermatozoon. But we can 

 destroy the membrane by shaking it. If we then add sperm to 

 such eggs, the spermatozoa enter, cause a second membrane 

 formation (in which the membrane fits tightly around the egg) 1 

 and the eggs develop at room temperature without requiring 

 any further treatment with the hypertonic solution; ..." 



(a) Membrane Production. If the facts are as Loeb states 

 them we can only come to the decision that no change in the 

 physiological state of the cytoplasm has occurred; at least it 

 has not rendered the cytoplasm unfertilizable. If we could 

 eliminate the membranes from all the eggs we should be able to 

 obtain practically as high a percentage of developing eggs as 

 before the butyric acid treatment. Furthermore if the sper- 

 matozoon carries a lysin-like substance that causes membrane 

 formation there is no reason that we should not get a second 

 membrane formation around the egg following insemination. 



The first point for consideration is the character or degree of 

 membrane production. This is essential. We have already 

 seen that there is a decided quantitative aspect to the process 

 and that the power of fertilization runs parallel with this. 



Quoting further from Loeb ('15, p. 262): 



"The treatment of the eggs of Arbacia with butyric acid 

 leads to the formation of a membrane which varies considerably 

 in the eggs of the same female. . . . Since the membrane called 

 forth by butyric acid is not always plainly visible, it is a pre- 

 requisite that always one set of such eggs should be set aside as 

 controls to ascertain whether or not all the eggs disintegrate 

 rapidly (if no second treatment is given to them). Only if they 

 all disintegrate rapidly have we any guarantee that in all of 

 them the membrane formation has been effective." 



Loeb however fails to consider that disintegration is by no 

 means a test for membrane production. Eggs exposed to 

 butyric acid for slightly longer than the optimum time for 

 membrane production do not produce membranes yet they 



1 Loeb, '15, has later retracted this second membrane formation. 



