OF MICRO-ORGANISMS. 77 



those of the bee, in the seminal reservoir of the fe- 

 male, remain alive for several years. The seminal ele- 

 ments of mammifers live for quite some time in the 

 genital passages of the female. Balbiani has found 

 living spermatozoids in the ducts of a she-rabbit twenty 

 hours after coition. Ed. vanBeneden, Benecke, Eimer, 

 Fries, have observed that the sperm retains its prop- 

 erties in the uterus of bats for several months. 



Another remarkable circumstance is, that the cop- 

 ulation of the two sexual elements is not without anal- 

 ogy to the copulation of the two animals from which 

 they originated. The spermatozoid and the ovule, to 

 some extent, repeat on a small scale what the two in-, 

 dividuals perform in their larger sphere. Thus, it is 

 the spermatozoid that, in its capacity of male element, 

 goes in quest of the female. It possesses, in view of 

 the journeys it has to make, organs of locomotion that 

 are lacking in the female and are useless to it. The 

 spermatozoid of man and of a great number of mam- 

 mifers is equipped with a long tail, the end of which 

 describes a circular conical movement, which together 

 with its rotation about its axis, determines the forward 

 motion of the spermatozoid. The same mode of pro- 

 gression is seen in the zoospores of Algae and in Masti- 

 gophores, which are armed with flagella; the move- 

 ments of the spermatozoid have been not improperly 

 compared to those of a Flagellate. 



Other spermatozoids like those of the Triton and 

 Axolotl are provided with a different kind of locomo 

 tive apparatus; it consists of an undulatory membrane 

 that acts like a real fin; the spermatozoid moves for- 

 ward without turning about on its axis. 



There has been much discussion as to the nature 

 of the forces that account for the movements of the 



