FERTILIZATION, CORTEX, AND VOLUME. 



OTTO GLASER. 



I. 



The initiation of development is associated with alterations in 

 the cortex of the egg. Some of these changes are visible under 

 the microscope ; others are matters of inference. But writers on 

 the mechanism of fertilization by no means agree in their interpre- 

 tation of either the observed or the postulated phenomena. 

 Indeed, there is uncertainty even in the realm of direct observa- 

 tion. For example, the fertilization membrane is considered by 

 some as an epigenetic structure formed at the moment of impreg- 

 nation, whereas others claim that fertilization merely results in 

 changes by which a preformed membrane is rendered visible. 

 Again there is the question of volumes. In 1913 and '14, I 

 claimed for Arbacia as well as Asterias, an immediate loss of 

 volume at fertilization; in 1921 Chambers claimed a constant 

 volume and even an actual increase. 



In themselves these details do not appear very important. It 

 is not obvious just how current interpretations would be affected 

 if it were possible to convince everyone either that the fertilization 

 membrane is preexistent or formed de novo. Yet with respect 

 to volume, the case has practical consequences. It is true that 

 here too, no compulsion, theoretical in origin, or otherwise, 

 forces us to favor any particular assumption. Whether the egg 

 increases, decreases, or remains constant does not inevitably 

 involve any revision in theory. Of course, a decrease in volume 

 as well as an increase might result from individual one-way 

 mechanisms different in the two cases, whereas a constant volume 

 might merely signify the absence of relevant changes of any sort. 

 On the other hand, each of the three possibilities is conceivable 

 as the resultant of antagonistic processes, one or more of which 

 could be common to all. This, however, by no means implies 

 that it is immaterial, practically, which of the three things is true. 

 In our present state of knowledge, one of the three possibilities, 

 it happens, is capable of making a more significant comment than 



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