84 THE NEW AET OF BREEDING FISH. 



The observations of zoologists show, too, that in 

 the general harmony of nature, the fecundity of 

 animals is regulated, not only with regard to the 

 causes of destruction to which the young are exposed 

 before they become capable of reproducing their 

 species, but also in view of the chances of nonfecun- 

 dation to which the eggs are submitted, as the con- 

 tact of the eggs with the seminal fluid takes place 

 after they have been spawned and depends more or 

 less upon chance. Fish belong, for the most part, to 

 the category of animals among which there is no 

 act of copulation for reproduction, that being effected 

 simply by the ejection by the male of the milt or se- 

 men upon the eggs which have been spawned by the 

 female. 



To procure the development of the embryo, there- 

 fore, in the otherwise sterile eggs, the naturalist, in 

 the experiments of his laboratory, has only to imitate 

 that which happens normally in nature ; that is to 

 say, to bring them in contact with water charged 

 with milt ; impregnation, then, is soon effected, and to 

 procure this milt, as well as the eggs to be impregnated, 

 aU that is required is a light pressure of the abdomen 

 of the males and females, whose products are ma- 

 tured and whose lives will not be endangered by the 

 operation : or these products may even be procured 

 by opening the bodies of newly dead subjects, for the 

 eggs and the milt preserve their vitality for some 

 time after the death of the bodies containing them, 



