696 



MALE ORGANS OF GENERATION. 



Fig. 230. twentieth the whole length of 



the filament, and often slightly 

 curved at its anterior extremity. 

 In the frog and in reptiles gen- 

 erally, the spermatozoa are lon- 

 ger than in quadrupeds. In 

 Menobranchus, the great Amer- 

 ican water-lizard, they are of 

 very unusual size (Fig. 230, c), 

 measuring not less than 0.57 

 millimetre in length, about one- 

 third of which is occupied by 

 the head, or enlarged portion 

 of the filament. 



The most remarkable peculi- 

 arity of the spermatozoa, as seen 

 under the microscope, is their 

 rapid and energetic movement. 

 In a drop of fresh seminal fluid, 

 if kept sufficiently moistened 

 and at its normal temperature, 

 the numberless filaments with 

 which it is crowded are seen to 

 be in a state of incessant mo- 

 tion. In many species of ani- 

 mals, the movement of the sper- 

 matozoa strongly resembles that of a tadpole ; particularly when, as in 

 the mammalia, they consist of a short, well-defined head, followed by 

 a long and slender tail. The tail-like filament keeps up a constant lat- 

 eral vibratory movement, by which the spermatozoon is driven from 

 place to place in the seminal fluid, as a fish or a tadpole is propelled 

 through the water. In other instances, as in the Triton, or water lizard, 

 the spermatozoa have a continuous w r rithing or spiral-like movement ; 

 presenting a peculiarly elegant appearance when large numbers are 

 viewed together. 



It is this movement which gave origin to the name of spermatozoa, 

 to designate the filaments of the spermatic fluid. But, notwithstanding 

 its active character, and its resemblance in mechanism to the locomo- 

 tion of certain animals, it has no analogy with a voluntary act. 



The spermatozoa are organic forms, produced in the. testicles, and 

 constituting a part of their tissue; just as the eggs, which are pro- 

 duced in the ovaries, naturally form a part of the texture of these or- 

 gans. Like the egg, the spermatozoon is destined to be discharged 

 from the organ where it grew, and to retain, for a certain time after- 

 ward, its vital properties. One of these properties is its power of move- 

 ment ; but this does not indicate the possession of independent vitality, 

 and is not even necessarily a proof of its animal origin. The move- 



SPERM ATOZO A. a. Human, b. Of the rat. 

 c. Of Menobranchus. Magnified 480 times. 



