M. C. CHANG 127 



zona pellucida, but our knowledge of the physiology of the Fallo- 

 pian tube, the corona radiata, the zona pellucida, and the vitel- 

 line membrane is very elementary. 



The activation or cleavage of eggs in vivo and in vitro without 

 the stimulation of sperm is fairly common, but its mechanism is 

 not known. Although parthenogenetic development to the blas- 

 tocyst stage or to newborn can be achieved by subnormal tem- 

 perature treatment of eggs, there may be still more effective 

 methods to be discovered. The physiological difference between 

 artificial activation and fertilization should be further inves- 

 tigated. 



Sperm penetration of the vitellus, the formation of male and 

 female pronuclei, and the maturation and conjugation of pronu- 

 clei have been observed, but their physiological properties and 

 their interactions are completely unknown. Even the morphology 

 of conjugated pronuclei and their subsequent division are far 

 from clear. 



The fertilizability of eggs and its physical basis, the blockage 

 of polyspermy and its chemical nature, and the possibility of 

 the artificial induction of polyspermy and its subsequent events 

 are all obscure. 



In view of the possibility of a complex of enzymic reactions at 

 fertilization, the role of sperm hyaluronidase at fertilization has 

 been erroneously interpreted. At present, we have certain knowl- 

 edge about what hyaluronidase or hyaluronidase inhibitor may 

 not do, but we do not know the actual function of sperm hyalu- 

 ronidase. 



It seems that agglutination of mammalian spermatozoa is not 

 a specific reaction to eggs but rather a general reaction. The ag- 

 glutination of sperm in relation to the fertilizing capacity of 

 sperm is uncertain and its relation to the fertilization reaction of 

 mammalian eggs is far from understood. 



REFERENCES 



Amoroso, E. C, and A. S. Parkes. 1947. Effects on embryonic develop- 

 ment of x-irradiation of rabbit spermatozoa in vitro. Proc. Roy. Soc. 

 (London), B134, 57-78. 



