SPERMATOZOON 45 



is one of the smallest cells in the animal body. The 

 seminal fluid is called "sperm" or "the male seed.' 

 Sperm, like saliva or blood, is not a simple fluid, but 

 is a thick agglomeration of innumerable cells swim- 

 ming about in a comparatively small quantity of fluid. 

 It is not the fluid, but the independent male cells, 

 which swim in it, that cause conception. They have, 

 as a rule, "a peculiarly lively motion.' In most 

 animals, the spermatozoa have a very small naked 

 body, inclosing an elongated nucleus and a long thread 

 like tail, hanging from it. It was long before we could 

 recognize that these structures were simple cells. We 

 now know that the spermatozoa are nothing but 

 simple and real cells of the kind we call "ciliated' 

 cells, equipped with cilia or "lashes.' 



The body of the spermatozoon is divided into 

 "head," "trunk" and "tail." The head is merely 

 the oval nucleus of the cell; the body or middle part 

 is an accumulation of cell matter and the tail is a 

 thread-like prolongation of the trunk or body. The 

 form of the spermatozoon is not peculiar to it; cells 

 with similar forms are found in various other parts 

 of the body. Such forms as the spermatozoon are 

 called caudate or tailed cells. See Haeckel, Evolution 

 of Man, p. 52-53. 



"The spermatozoa," says Professor Martin, "are 

 motile bodies about l/500th of an inch in length ; they 

 have a flattened, clear body or head and a long vibra- 

 tile tail or cilium ; the portion of the tail nearest the 

 head is thicker than the rest, and is known as the neck. 

 The mode of development of a spermatozoon shows that 

 the head is a cell-nucleus and the neck and tail a 



