SYNGAMY 249 



at a certain period, it binds the spermatozoon to the surface of the egg; 

 and the spermatozoon, without necessarily penetrating the egg at all, 

 releases the activity of the fertilizin within the egg, this resulting in 

 development. In brief, the activating substance is already present in 

 the egg and is not brought to it by the spermatozoon. It may be incited 

 to activity by the spermatozoon but by other agencies as well. According 

 to Woodward (1918) and Glaser (1921), the agglutinating material and 

 the parthenogenetic agent are two distinct substances. 



Among other immediate physiological consequences usually following 

 fertilization may be mentioned: an increase in permeability to oxygen, 

 CO2, pigments, water, alkalies, vital dyes, and certain other substances; 

 an increase in the rate of oxidation; an increase in viscosity, centering in 

 the sperm aster; a rise in electrical conductivity; the loss of fertilizin 

 (Lillie, 1919). Just (1920) points out that most of these changes are not 

 incident to the fertilization reaction per se but are primarily changes 

 bound up with the egg's division. 



In this connection one may be cautioned against the assumption that 

 normal activation is complete when the spermatozoon has gained entrance 

 to the egg. Morgan (1924/) cites the fact that, if an inseminated egg be 

 cut into two pieces in such a way that one fragment contains the egg 

 nucleus and the other the sperm nucleus, only the latter develops; he 

 therefore emphasizes the inadequacy of theories of fertilization which 

 terminate with the entrance of the spermatozoon. 



Conclusion. — Syngamy is a mutual process: that which undergoes 

 development following syngamy is a zygote — the fusion product of two 

 gametes, no matter how dissimilar these may have been in their morpho- 

 logical and physiological differentiations. Syngamy has two important 

 results: there is a physiological alteration with profound effects upon the 

 behavior of the protoplasts concerned, and there is a nuclear reorganiza- 

 tion which is no less significant. In view of the cardinal importance of 

 the latter change with respect to current theories of heredity, it should 

 be remembered that in the syngamic nuclear union two monoploid sets of 

 chromosomes are brought together and form a diploid complement in the 

 zygote nucleus; and since every chromosome of this complement divides 

 equationally in every somatic mitosis throughout the development of the 

 resulting individual, every nucleus in this individual contains a descendant 

 of every chromosome originally present in the zygote.^^ 



As the finer details of syngamy and the significance of its results 

 become better understood, the aptness of Huxley's (1878) often quoted 

 simile, in which he compared the organism to "a web of which the warp 

 is derived from the female and the woof from the male," becomes increas- 

 ingly striking. 



^' Only typical "diploid" organisms are considered here. The phenomena in 

 "polyploid" organisms are essentially the same except for the number of chromosome 

 sets present (see p. 339). 



