SPERMATOGENESIS— INSEMINATION 177 



seminal fluid. The rate at which they progress has been 

 estimated at 3'6 millimetres per minute.* BischofE ^ found 

 spermatozoa at the top of the oviduct in the rabbit nine or ten 

 hours after coition. 



It is probable that the ejected spermatozoa continue to 

 undergo movement, as a general rule, so long as they retain 

 their vitahty, the rate of movement becoming gradually 

 diminished and ceasing altogether shortly before death. In 

 bats, however, during the period of hibernation the sperms 

 become quiescent without dying, their vigour being restored 

 in the spring when they conjugate with the ova.* It is 

 exceedingly probable also that in the spotted viviparous 

 salamander and the other animals referred to below (p. 186), in 



Fig. 49. — Diagram illustrating wave-like movement of swimming 

 spermatozoon. (From Nagel.) 



which the male cells retain their vitahty for long periods, these 

 must at such times remain quiescent, for otherwise their store 

 of energy would soon become exhausted. 



The spermatozoa swim by means of their tails. The move- 

 ment is represented in the accompanying figure (taken from 

 Nagel),* which shows the successive positions assumed by the 

 sperm in a state of locomotion. A wave of movement first 

 makes its appearance in the forepart of the tail, and then rapidly 

 travels backwards to the end, to be succeeded by a fresh wave 

 which follows the same course. It would seem that the driving 



' Lott, Anatomic und Physioloyie des Cervix Uteri, Erlangen, 1871. Ac- 

 cording to Adolphi ("Ueber das Verhalten von Schlungenspermien in 

 stromender Flussigkelten," Anat. Anz., vol. xxix., 1906), the spermatozoa of 

 the adder swim at the rate of 50 /i. to 80 /i. per second. 



^ BischofE, Die Entwickelung des Kaninohen-Eies, Giessen, 1842 



' See p. 136. : 



* Nagel, Handbuck der Physiologic des Menschen, vol. ii., Braunschweig, 

 1906. 



M 



