CHAPTEE XVIII. 



PERIOD OF GESTATION. 



THE duration of the period of gestation in mam- 

 mals is apparently determined by various causes that 

 we are as yet, from the obscurity of their action, un- 

 able to define. 



That it bears some relation to the size of the ani- 

 mal is shown by the following instances, which have 

 been compiled from various sources ; * and Mr. Darwin 

 states that it has been observed in Germany that " the 

 period of gestation is longer in large-sized than in 

 small-sized breeds of cattle." 2 



The period of gestation is approximately as fol- 

 lows : Elephant, twenty to twenty-three months ; 

 giraffe, fourteen months ; dromedary, twelve months ; 

 buffalo, different varieties, from ten to twelve months ; 

 ass, twelve months ; mare, eleven months ; cow, two 

 hundred and eighty-five days ; bear, six months ; rein- 



1 Van Der Hoeven's " Zoology," vol. ii. ; " ^Economische ncugikund 

 Verhandl," quoted in Johnson's " Farmer's Cyclopaedia," and Quarterly 

 Journal of Agriculture, vol..x., p. 287; Dunglison's "Human. Physiol- 

 ogy;" Johnson's " Cyclopaedia," article "Gestation," by Dr. E. R. 

 Peaslee; "Encyclopaedia Britannica," article "Animal Kingdom," by 

 Prof. Wilson. 



9 "Animals and Plants under Domestication," vol. ii., p. 387. 



