INHERITANCE OF ACQUIRED CHARACTERS 209 



ence is one due to the environment of the individual. Those 

 in the sea find adequate salts from which to develop their 

 coats of mail. Those in fresh water do not find this, while 

 those in river mouths and other brackish situations develop 

 armature in intermediate degrees. In the genus Eucalia, a 

 stickleback confined to fresh waters of the Middle Western 

 States, plates are never developed. 



The Loch Leven trout, Salmo levcnensis, is distinguished 

 from the brook trout of England, Salmo eriox (/an'o), in its 

 native waters by certain obvious characters. These disappear 

 when the eggs are planted in brooks in England or in California, 

 and the species develops as the common English brook trout. 

 But it is conceivable that the obvious or ontogenetic traits of 

 the Loch Leven trout are not the real or phylogenetic distinc- 

 tions, and that the latter, more subtle, engendered through in- 

 dividual variation, inheritance, selection, and isolation, really 

 exist, although they have escaped the attention of ichthy- 

 ologists. 



After the Loch Leven trout was planted in the Yosemite 

 Park in 1896, it remained for nine years unnoticed. In 1905 

 individuals sent to Stanford University were, so far as could 

 be seen, exactly like English brook trout. But it is conceivable 

 that differences in food and w r ater have caused slight ontogenetic 

 distinctions. It is certain that in isolation from all parent 

 stocks they will in time develop larger differences w T hich, after 

 many thousand generations, will be specific or subspecific. At 

 present, these trout are quite unlike the native rainbow trout 

 (Salmo irideus gilberti} of the Yosemite. The ontogenetic char- 

 acters will perhaps approach those of the latter, but the phylo- 

 genetic movement may be in quite another direction. 



Another ontogenetic species is the little char or trout (Sal- 

 vdinus tudes Cope) from Unalaska. In Captain's Harbor, Una- 

 laska, the Dolly Varden trout, Salvclinus malma, swarms in 

 myriads, in fresh and salt water alike, reaching in the sea a 

 weight of from six to twelve pounds. A little open brook, which 

 drops into the harbor by an impassable waterfall, contains also 

 an abundance of Dolly Varden trout, mature at six inches and 

 weighing but a few ounces. This is Salvelinus tudes. In the 

 harbor the trout are gray with lighter gray spots, and fins scarcely 

 rosy. In the brook, the trout are steel blue, with crimson spots 

 and orange fins, striped with white and black. In all visible 



