SPECIFIC EGG AND SPERM SUBSTANCES 

 AND ACTIVATION OF THE EGG 



CHARLES B. METZ*: oceanographic institute, 



FLORIDA STATE UNIVERSITY, TALLAHASSEE 



At fertilization the egg undergoes a complex series of morpho- 

 logical, physiological, biochemical and, in many cases, morpho- 

 genetic changes that ultimately lead to the differentiation of the 

 new individual. These initial changes constitute the activation of 

 the egg. Under favorable conditions they proceed in an orderly 

 sequence, and the precision of this sequence suggests that the 

 activation changes are interrelated and that they all follow from 

 a few or even a single reaction between the egg and the sperm. 

 Many consider this problem of the activation initiating mecha- 

 nism the central problem of fertilization, but it should be borne 

 in mind that fertilization involves other problems as well. Thus 

 fertilization is characterized by a high order of specificity. This 

 reaches its ultimate expression in those hermaphroditic organ- 

 isms that exhibit self sterility. Finally the sperm must approach 

 the egg, penetrate any extraneous egg membranes, attach to and 

 penetrate the egg surface. 



These problems of fertilization may be attacked experimen- 

 tally in several ways and of these the one most likely to provide 

 solutions would appear at present to be the study of the role of 

 specific egg and sperm substances in fertilization. The literature 

 of fertilization recounts many attempts to extract a "fertilizing 

 substance" from sperm or to activate eggs with dead spenn. How- 

 ever, none of these efforts appears to have stood the test of criti- 

 cal examination in spite of initial claims of success. Even the most 



** These studies have been supported in part by grants from the National 

 Institutes of Health, the American Cancer Society, and the National Sci- 

 ence Foundation. 



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