18 THE BREEDING OF ANIMALS 



the body of the female. In fishes, the spawn con- 

 taining the eggs is deposited in the water by the female, 

 and the fertilizing fluid of the male containing the sper- 

 matozoa is also deposited in the water on or near the female 

 spawn. In all higher animals, including the domestic 

 animals, the fecundating fluid of the male reaches the 

 egg inside the body of the female, and the process of ferti- 

 lizing the egg is accomplished within the generative organs 

 of the female. 



20. Oviparous animals. In some species of animals, 

 including birds, fishes, most reptiles, and nearly all 

 invertebrates, the eggs are deposited outside the body 

 either before or after fertilization. In the bird family, 

 which includes all the domestic fowls, the egg is fertilized 

 inside the body of the mother, where it undergoes some 

 slight development before being eventually deposited or 

 laid outside the body of the female. Animals of this 

 class are called oviparous, to distinguish them from vivip- 

 arous forms which bring forth their young alive. The 

 future development of the egg deposited by oviparous 

 animals is dependent upon its being supplied with favor- 

 able conditions of heat and moisture. This period of 

 development outside the body is called the period of 

 incubation and is, in many ways, similar to the period 

 of gestation in viviparous animals. Animals in which 

 the fertilized egg develops inside the body are called vivip- 

 arous, and this development proceeds to a point where 

 the young animal is, in the main, able to carry on a sepa- 

 rate and independent existence. The period of growth 

 inside the body of the mother in mammalian animals is 

 called the period of gestation, and during this period 

 the developing embryo is gradually fitted for an inde- 

 pendent life outside the protecting body of the mother. 



