182 ORGANISED FLUIDS. 



SPERMATOZOA. 



The spermatozoa * are the most distinctive, as \vell as the 

 most interesting, constituent of the semen, and once detected, 

 the nature of the fluid under examination can no longer be 

 doubted. 



Each spermatozoon consists of two portions, an expanded 

 part, to which has been assigned the several names of " disc," 

 " head," and " body," and an attenuated extremity, which is 

 called " tail." 



The spermatozoa present great varieties in size and form : 

 these variations are for the most part constant in a natural 

 family and genus, and are always so in a simple species : thus 

 a knowledge of the particulars of form and size of the seminal 

 animalcules is frequently sufficient to distinguish many groups, 

 genera, and individuals from each other : spermatozoa are, 

 therefore, capable of affording assistance in classification. 



Form. 



In the class Mammalia especially, with which, in this paper, 

 we are chiefly concerned, the spermatozoa vary greatly in 

 shape; but in several of the more natural groups of that 

 class, one determined form and magnitude may be detected 

 throughout the different species constituting such groups. 



* In reference to the discovery of the spermatozoa, the following passages 

 are contained in Leeuwenhoek (Opera, t. iv. p. 57.) : " N". Hartsoeker 

 (Prseven der Doorsichikunde, a. Specimina dioptrices, p. 223.) says that 

 he made known the spermatic animalcules in 1678, in the " Journal des 

 Savants." I attribute the discovery to Hamm. He brought me in 1677 

 some gonorrheal matter, in which he found animalcules with a tail, which, 

 according to him, were produced by the effect of decomposition. I after- 

 wards examined fresh human semen, and I then perceived the same 

 bodies. They were in motion, but in the liquid portion ; in the thick 

 part they remained immoveable. They were smaller than the corpuscles 

 of the blood, rounded, obtuse before, pointed behind, with a tail five or 

 six times as long as the body." The description of Leeuwenhoek appeared 

 for the first time in the Philosophical Transactions, December 1677 and 

 January and February 1678. 



