the Seminal Fluid of Animals. 339 



the seminal fluid of man, the dog, ass, horse, bull, goat, hare, 

 and frog, a partial difference of form will certainly be observed 

 between the latter and those which I have discovered in the in- 

 vertebrate animals already mentioned ; in other respects, how- 

 ever, the former as well as the latter are furnished with pedun- 

 cles, from which they detach themselves on the admixture of 

 water with the semen, and they do not possess such an internal 

 organization as would authorize us to place them in the class of 

 self-existent animals. The organized parts in the semen of the 

 fish differ still more widely from the organized products found 

 in the seminal fluid of the invertebrate animals. These have 

 always appeared to me merely as simple non-pedunculated ve- 

 sicles, from 0,0011 to 0,1600 of a millimeter in diameter. In 

 undiluted semen, they often lie so close together that they can- 

 not be distinguished from each other. In this instance, the ve- 

 sicles which constitute the most important part of the semen, 

 which in all the other classes of animals are combined together 

 in masses covered by a common integument, and escape singlv 

 from this envelope only at a certain period, appear to have been 

 contained in the fluid portion of the semen from the very com- 

 mencement. 



" Hitherto, the motions exhibited by the organized parts of 

 male semen, have been looked upon as analogous to those of the 

 true infusory animalcules. From these, however, they differ 

 very much. The infusory animalcules, it is true, exhibit con- 

 tinued motions ; but from time to time they pause, in general, 

 however, only for a moment, for the purpose of taking nutri- 

 ment. But we never observe these interruptions of motion from 

 internal causes in the bodies found in the semen. Those met 

 with in the semen of the ferae and birds, swing back and for- 

 wards like a lifeless pendulum, as long as they remain attached 

 to their peduncles. When detached, they range continually over 

 the field of the microscope, without stopping anywhere. The 

 long peduncles of the discs, in the seminal fluid of the snail, 

 twist and bend themselves ; still, merely in the same way as dead 

 elastic filaments, which attract water, which pass from a state of 

 dryness to a state of moisture, and vice versa. The motions of 

 the vesicles in the semen of fishes resemble the molecular mo- 

 tion described by Brown, except that in matured semen it is 



