and of its chief Periods in the Hippopotamus. ISO 



Zoological Gardens was born January 7, 1872*, and was 

 begotten May 27, 1871. It was a female, and died on the 

 10th January, 1872; the gestation was 227 days, being 10 

 days shorter than in the case of the male offspring. 



On November 5, 1872, the Secretary reports " the birth of 

 a third hippopotamus {Hippopotamus amphibius), which had 

 taken place that day in the Society's Gardens at 7 A.M. 

 The period of gestation in the present instance had been eight 

 calendar months less four days, according to the keeper's 

 observations " f. 



The coitus here is noted as on March 9, 1872J. The off- 

 spring was a male ; and the gestation was five days longer 

 than in the case of the first male, and fifteen days longer than 

 in the case of the female offspring. 



Since this birth the mother has ceased to breed ; she is four 

 years younger than the male. The female hippopotamus in 

 the menagerie at Amsterdam produced young as soon as she 

 was full-grown. 



The term of growth of the hippopotamus appears to be 

 about five years ; it extended, in the instance of the male 

 born in midsummer 1849, as to length, to the year 1854 ; but 

 the well-fed animal gained in bulk during some following 

 years. The procreative period, commencing probably in 

 1854, was continued up to the year 1872, and perhaps a 

 few years later, say to 1875, when the animal had attained 

 the age of 26 years ; this would leave a period of four years 

 for old age. 



An approximate conclusion as to the natural term of life in 

 mammals may be made upon knowledge of the duration of 

 one of the well-marked periods of existence. These arc three, 

 viz. the " preprocreative," the u procreative," and the " post- 

 procreative" periods. In the human subject the first is modi- 

 fied to a small extent by latitude and climate. Taking an 

 average as at 18 years, the procreative period may be set 

 down as at three times that extent, carrying on the life-term 

 to 72 years. If the postprocreative equals the preprocreative, 

 life will extend to 90 years. 



If the first period of life be characterized by the acquisition 

 of full growth, then a man might survive as long after the 

 procreative period, ending say at 75 in the male, as he had 

 Hved to acquire maturity and complete ossification, say at 30 

 years, and so reach the rare term of 105 years. 



* See "Notes on the Visceral Anatomy of the Hippopotamus," by J. \Y. 

 Clark, F.R.S., Proc. Zool. Soc. 1872, p. 185. 



f Report on the additions to the Society's Menagerie, by the Secre- 

 tary, Proc Z.x.l. Soc. L872, p. 795. f Ibid. p. 819. 



Ann. & May. N. Hist. Ser. 5. Vol. iv. 14 



