504 PLAIN FACTS FOR OLD AND YOUNG 



brought, then, for a solution of this problem, to a con- 

 sideration of the question, What is the object of the 

 reproductive act in those members of the animal king- 

 dom just below man in the scale of being? Let science 

 tell us; for zoologists have made a careful study of 

 this subject for centuries. 



We quote the following paragraphs from one of the 

 most distinguished and reliable of modern physiolo- 

 gists,* the facts which he states being confirmed by all 

 other physiologists: 



"Every living being has a definite term of life, 

 through which it passes by the operation of an invari- 

 able law, and which, at some regularly appointed time, 

 comes to an end. . . . But while individual organisms 

 are thus constantly perishing and disappearing from 

 the stage, the particular kind, or species, remains in 

 existence. . . . This process, by which new organisms 

 make their appearance to take the place of those which 

 are destroyed, is known as the process of reproduction, 

 or generation. 



"The ovaries, as well as the eggs which they con- 

 tain, undergo, at particular seasons, a periodical de- 

 velopment, or increase in growth. ... At the approach 

 of the generative season, in all the lower animals, a 

 certain number of the eggs, which were previously in 

 an imperfect and inactive condition, begin to increase 

 in size, and become somewhat altered in structure." 



"In most fish and reptiles, as well as in birds, this 

 regular process of maturation and discharge of eggs 

 takes place but once in a year. In different species of 

 quadrupeds, it may take place annually, semiannually, 

 bi-monthly, or even monthly; but in every instance, it 

 recurs at regular intervals, and exhibits accordingly, 

 in a marked degree, the periodic ':'ha.racter which we 



* Dalton I 



