98 American Fisheries Society 



with its high percentage of impregnation, the fish cultur- 

 ist, by his method of fertilization alone, saves eggs that 

 would otherwise perish. The fish culturist saves without 

 a doubt, but not by his method of fertilization, for that 

 is no more perfect than in nature. It is in truth, proba- 

 bly less perfect. In nature the eggs are laid only when 

 thoroughly ripe and only in the presence of the fertiliz- 

 ing male. In spite of all his care the fish culturist, on the 

 other hand, spawns females that are unripe and over- 

 ripe and loses a considerable percentage in this way. He 

 often finds eggs, naturally laid, a large percentage of 

 which are dead, and may assume that these have not been 

 fertilized. Under normal conditions the eggs that are 

 unfertilized do not undergo cleavage and do not therefore 

 form a blastoderm. If eggs are collected from natural 

 waters shortly after they have been laid and while all of 

 them are still living, it is found that practically all of 

 them have undergone cleavage or that this has proceeded 

 until a germinal disc has been formed. This in the early 

 stages is the only criterion of fertilization. If the eggs 

 are collected somewhat later many of them are dead and 

 partly decayed and it is then impossible to tell whether 

 or not they have been fertilized. To assume that they 

 have not been fertilized is to ignore all that we know of 

 eggs collected shortly after they have been naturally laid. 

 I have collected from the natural waters the recently laid 

 eggs of many fish and have failed to find any consider- 

 able number unfertilized. The gain of the fish culturist 

 is therefore not in a higher percentage of fertilization, 

 but rather in the protection afforded the eggs after fer- 

 tilization. 



The eggs may be laid in nests prepared by the male 

 parent and are in that case protected by him until they 

 hatch, or as in case of the black bass, until the young are 

 well grown. Nearly one fifth of the species of fishes that 

 occur in Michigan are known to build nests, and give 

 their eggs, by this means, a protection analogous to that 

 afforded by the fish-culturist. But the majority of fishes 

 build no nests and their eggs suffer from many enemies. 



