I 404 ] [Book IX. 



CHAP. XLII. 



THE GESTATION AND BIRTH OF ANIMALS* 



Varieties in the Production of Animals. Proportion of Males to Fe- 

 malts. Growth of the Foetus. Oviparous jfnimals. Mode of 

 Exi/icnce before Birth. Weight of a new born Infant.Mifcella- 

 neous Calculations concerning (he Proportion of Births to that of 

 Deaths in Infancy, &c . 



WE have hitherto been occupied in confi- 

 dering the functions which relate to the exift- 

 cnce and welfare of animals, let us now direct our 

 attention to thofe which, nmidft the decay of indivi- 

 duals, prefer ve the continuance of the fpecies. 



Among the more minute, and imperfect animals, 

 there are fome which may be multiplied from frag- 

 ments of the fame fpecies, as the polypus j others 

 grow from the bodies of their parents, and are in 

 due feafon fet at liberty to feek nourifhment for them- 

 felves j fome animals, at a certain period of their 

 exiftence, naturally divide into feveral parts, each of 

 which afterwards becomes a perfect animal of the fame 

 race. 



As we afcend in the fcale of animal exiftence, a 

 difference of fex prefents itfelf as a leading distinction. 

 We find fome races of animals, of which every in- 

 dividual is pofTefled of both male and female organs; 

 others, among which a fingle female breeds for a 

 whole community, and among which there are very 

 few individuals pofTefTed of fexual organs. In general, 

 however, about half x the individuals of a fpecies are 

 males and half females. 



It 



