178 THE PHYSIOLOGY OF REPRODUCTION 



at this time are dormant, but regain their vitality on the application 

 of warmth.'^ 



The spermatozoa of some warm-blooded animals will stand 

 considerable variation in temperature and still retain their vitality. 

 Thus they have been known to live for many hours at ordinary 

 room temperature ; but cold, while it reduces their motility, tends 

 to prolong their life, the motility being regained under a higher 

 temperature. Heape states that some seminal fluid of a dog was 

 sent to him by post in a glass tube, and on being examined eighteen 

 hours after it was obtained, fully half the spermatozoa were found 

 to be active and vigorous, while increased' warmth stimulated to 

 activity those which showed signs of sluggishness but did not revive 

 the remainder. 



Chelchowski,^ in describing the methods adopted in the artificial 

 insemination of mares, lays stress upon the necessity of keeping the 

 seminal fluid warm, and states that, if this is done, it is possible to 

 keep the sperms alive for twenty hours; but it is possible that 

 Chelchowski may have mistaken absence of movement under a low 

 temperature for death. 



The experimental work of Wolf and of other recent investigators 

 is described below in the chapter on fertility (p. 650). 



The case of bats, which has been referred to above, has a parallel 

 in certain cold-blooded animals. Thus, according to Rollinat,^ in 

 snakes belonging to the species Tropidonotus viperinus the females 

 are usually inseminated in the autumn, whereas the eggs are not 

 laid until the beginning of the following summer. Also in the case 

 of the spotted viviparous salamander (Salamander maculosa), after 

 the birth of the young, which occurs about the month of May, a 

 new batch of ova pass into the oviducts and are fertilised (prior to 

 the commencement of the sexual season) by spermatozoa which 

 were introduced in the July of the previous year, and thereafter 

 stored in the uterus.* It is obvious that in both these cases the 

 spermatozoa retain their vitality in the female for periods of many 

 months. 



In animals like the earthworm, in which the spermatozoa are 

 stored in special reservoirs known as spermathecae, it is probable 

 that they retain their vitality for long periods. Lang ^ has shown 



1 See Eimer and other references given on p. 131. 



2 Chelchowski, Die Sterilitdt des Pferdes, Wien, 1894. See also Lewis, " The 

 Vitality of Eeproductive Cells," Bull. 96, Agric. Exper. Stat., Oklahoma, 1911. 



2 Eollinat, "Sur I'Accouplement des Ophidiens a la Fin de rEt6 et au 

 Commencement de I'Automne," Bull. Zool. Soa. France, vol. xxiii., 1898. 



■• Sedgwick, Student's Te.vt-Booh of Zoology, vol. ii., London, 1905. 



" Lang, "tlber Vorversuohe zu ITntersuchungen Tiber die Varietaten- 

 bildungen von Helix hortensis Miiller aijd Helix nemoralis L.," Festschr. zum 

 siebzigsten Geburtstage von Ei-nst Haeckel, Jena, 1904. 



