1890.] Embryology. 89 
which has been slowly augmented and fixed by inheritance.2? Even 
certain species of fishes, when well fed and kept in confinement, not 
only spawn several times during a season, instead of only once, as I 
am informed by Dr. W. H. Wahl, but also when kept from hibernat- 
ing, as he suggests, tend to vary in the most astounding manner. The 
wonderful results of Dr. Wahl, attained in the comparatively short 
period of six years, show what may be done in intensifying the mon- 
strous variations of Japanese gold-fishes, through selection, confine- 
ment in tanks and aquaria, with comparatively limited room tor 
swimming, plenty of food, etc., all of which conditions tend to favor 
growth and metabolism, and the expenditure of energy under such 
wholly new and restricted conditions as to render it almost certain, as 
he thinks, that these factors have something to do with the develop- 
ment of the enormous and abnormally lengthened pectoral, ventral, 
dorsal, double anal and caudal fins of his stock. Some of the races of 
these fishes have obviously been affected in appearance by abundant 
feeding, as is attested by their short, almost globular bodies, protuber- 
ant abdomens, and greedy habits, as I have observed in watching 
examples of this short-bodied race living in Dr. Wahl’s aquaria. In 
these last instances we are brought face to face with modifications 
occurring in fishes under domestication which are infinitely in excess, 
morphologically speaking, of anything known amongst any other 
domesticated animals. That the abundant feeding and exposure to a 
uniform temperature during the whole year, and confinement in com- 
paratively restricted quarters, has had something to do with the genesis 
of these variations, through an influence thus extended upon the meta- 
bolism affecting the growth of certain parts of the body, which have 
tended to become hereditary, there can scarcely be any doubt.’ 
That such changed conditions would also favor variability to a high 
degree we cannot doubt. That, moreover, the passive or idle plasma 
3 The only possible explanation of the phenomenon of the after-effect of the first 
the viviparo upon al] subsequen 
turbance of the metabolic habit of the maternal organism by that offspring during the 
3 Since the foregoing was written, I have been able, through the ee e 
my friends, Mr. W. P. Seal and Dr. Wahl, who have supplied me with fresh material, to 
very my mepecion —— ee of the highly modified races of Japanese 
ll di P usual and unmodified type 


found in in open rivers. From careful dissecti 
a aaen has pgmn asked degeneration adenine 

