184 ORGANISED FLUIDS. 



may be briefly noticed. At the junction of the body and 

 tail of each spermatic animalcule an enlargement exists, the 

 excessively attenuated caudal extremity being curved spirally 

 round the body. 



The effect of water in modifying the form of the sperma- 

 tozoa is remarkable, it frequently causing them, when ap- 

 plied in large quantities, to coil up and form themselves into 

 rings : this effect of the application of water is supposed to 

 depend upon some hygroscopic property possessed by the 

 spermatozoa. 



Frequently the spermatozoa are seen to occur on the field 

 of the microscope grouped together in bundles, the bodies 

 all lying one way, and fitting by their concavities into each 

 other. (See Plate XVII.) This arrangement, as Avill be 

 seen hereafter, is connected with the evolution of the sper- 

 matozoa. 



Occasionally, in man and other animals, the head and tail 

 are separated from each other, and lie apart ; this separation 

 is doubtless either the result of violence or the effect of de- 

 composition. Henle * states that he has seen the tail move 

 independently of the head. 



Size. 



Much diversity exists in the size of the spermatozoa in 

 different animals, although but little difference can be de- 

 tected in those of the same individual. Wagner, however, 

 has made the observation that their magnitude varies greatly 

 in different individuals of the same species. These varia- 

 tions are, however, of course confined within certain narrow 

 limits. In the Mammalia the spermatozoa of man are amongst 

 the smallest, while those of the guinea-pig and rat are 

 amongst the largest hitherto discovered. In the birds the 

 seminal animalcules of the order Passeres are very large, and 

 especially those of the chaffinch. 



* Anat, Gen. p. 534. 



