XXIII 
THE ACTION OF THE SPERMATOZOON UPON THE EGG 
Il. THE COMBINATION OF ARTIFICIAL PARTHENOGENESIS AND 
FERTILIZATION WITH SPERM IN THE SAME EGG 
1. Two possibilities exist for the explanation of the activa- 
tion of the egg by a spermatozoon: either the spermatozoon 
carries a ferment or a-catalyzer into the egg which accelerates 
the rate of the chemical reactions in the egg; or it removes an 
obstacle to the development. The rdéle of the membrane forma- 
tion favors the latter idea, since it is not conceivable that all 
the diverse means by which development can be induced act 
as ferments; moreover, they only act provided they cause the 
membrane formation. Hence the membrane formation is the 
essential factor which induces development at least in the sea- 
urchin egg. This makes it rather improbable that the sperma- 
tozoon induces development by carrying a catalyzer into the 
egg (although it may carry enzymes for other purposes, e.g., 
heredity). 
This idea is supported by other facts. We know that the 
velocity of chemical reactions is increased if the quantity of 
the catalyzer is increased; and that if we double the quantity 
of the catalyzer the rate of velocity is increased in the ratio 
of either 1:2 or 1:1/2. The rate of chemical reactions during 
development can be measured by the rate of cell division of the 
egg, as is evidenced through the influence of temperature upon 
the rate of development (chap. iii). Hence if the spermatozoon 
caused development by carrying a catalyzer into the egg, the 
rate of segmentation should be either twice as fast or 1.4 times 
as fast if two spermatozoa enter the egg as if only one sper- 
matozoon enters. As is well known, cases occur in which two 
spermatozoa enter the egg. In such cases the egg divides into 
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