EXPLANATION OF THE PLATES. 



PLATE XVI. 



SEMEN. 



Fig. 1. The spermatic animalcules and " seminal granules " 

 contained in the human semen as ejaculated, mag- 

 nified 900 diameters, and to which are added several 

 spermatophori magnified to the same extent, and 

 introduced to render the representation of the de- 

 velopment of the spermatozoa of man more com- 

 plete. The larger seminal granules mostly contained 

 a single distinct nucleus, which renders it probable 

 that they are spermatophori in progress of develop- 

 ment. 



Fig. 2. Represents the several stages of evolution of the 

 spermatic animalcules of certhia familiaris (common 

 creeper) ; /, an adult spermatozoon taken from the 

 orifice of the vas deferens ; a, seminal granule pro- 

 cured from a very collapsed testicle in the winter 

 season ; b to k, spermatophori in different stages of 

 development taken from a testicle in summer, 

 during turgescence. 

 This figure is copied from Wagner's Elements of Special 



Physiology. 



k 2 



