218 WHAT IS LIFE 



algae, the conjugating cells are, in a morpho- 

 logical sense, precisely equivalent As we 



rise in the scale, the conjugating cells diverge 

 more and more, until in the higher plants and 

 animals they differ widely not only in form and 

 size, but also in their internal structure, and to 

 such an extent that they are no longer equivalent 

 either morphologically or physiologically."^^ 

 Again: In the higher life-forms "the gametes 

 differ widely in form and function, the macro- 

 gamete or ovum being a very large, quiescent 

 cell, while the microgamete or sperm is a very 

 minute and usually motile cell, typically pro- 

 vided with one or more flagella or cilia. "^^ 

 Jacques Loeb says that "only in respect to the 

 chromosome constitution are egg and sperm alike, 

 while they differ enormously in regard to the mass 

 of protoplasm they carry. "^^ 



The spermatozoa are naked cells, that is, cells with- 

 out membrane or protective covering. They are 

 detached glandular cells, rod-shaped, motile, ciliated, 

 of which each drop of seminal fluid may contain 

 millions. 



Of the millions of spermatozoa that press around 

 the ovum only one enters the egg and effects fertiliza- 



'1 The Cell, second edition, 229. 



'2 The Cell in Development and Heredity (1925), 256. 



'' The Organism as a Whole, 251. 



