88 REPORT ON ARTIFICIAL FISH-CULTURE. 



diictive elements^ and that tlie physiological puis- 

 sance of these same agents may be preserved 

 during a longer or shorter period after they have 

 been taken from the living bodies which have 

 given them existence. 



With a great number of inferior animals, the 

 parents part in the work of reproduction, consists 

 only in the formation and emission of these two 

 generic elements ; the egg is not impregnated till 

 after being spawned, it meets the spermatozoa, 

 the contact with which, necessary to endow it 

 with life, only takes place by the concurrence of 

 exterior causes, independent of the action of the 

 parents, for example, by the course of the cur- 

 rent in which the milt is deposited. The experi- 

 mentalist can, therefore, determine at will thi^ 

 physiological phenomenon, by mechanically mixing 

 the eggs and milt of these animals, and the same 

 result will be obtained by this process as by the 

 natural one. 



The observation 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 reproduc- 

 ing their species, but also in view of the chances 

 of non-fecundation to which the eggs are submitted 

 as the contact of the eggs with the seminal fluid 



