Human Physiology. 

 CHAPTER II. 



ANIMAL REPRODUCTION. 



Varieties of Modes of Reproduction in Animals Gemmation Fission 

 Rapid Multiplication Artificial Reproduction Production of Eggs 

 Masculine and Feminine Elements The Propagation of Fishes, Insects* 

 Birds, the Mammalia Size of Eggs. 



REPRODUCTION in animals is curiously analagous to the same 

 process in the vegetable kingdom. There are the same varieties 

 in the modes of multiplication and generation. The process of 

 generation in some of the lower animal organisations is exactly 

 like the throwing out of new bulbs in plants. The polypes 

 throw out buds which in a little while grow mouths, fringed 

 with cilia or tentacles, while they are still holding by stalks, 

 and drawing part of their nourishment from their parents. 

 When enough matured to get their own living they drop off. 

 swim away, and shift for themselves. This is gemmation. 



Fission is a common mode of propagation or multiplication 

 among the infusoria. An animalcule is seen to contract in a 

 ring around its centre; the fissure deepens, and it divides into 

 two distinct beings, which also divide, and so on multiplying 

 with surprising rapidity. It has been estimated that one of 

 these animalcules could produce by these successive divisions 

 in eight weeks a progeny of two hundred and sixty-eight millions. 

 This reproductive power is, however, almost rivalled by some 

 fishes and insects. The carp lays seven hundred thousand eggs 

 in a season, and lives two hundred years. The possible progeny 

 of a pair of these fishes is almost beyond computation. The cod 

 is said to produce from four to nine millions of eggs. The female 

 termite lays sixty thousand eggs a-day for a considerable period. 



Some of the lower animals may be multiplied artificially like 

 vegetables. Thus, if some species of the polypus are cut in 



