496 POPULAR SCIENCE MONTHLY 



trout are quite unlike the native rainbow trout (Salmo irideus gilberti) 

 of the Yosemite. The ontogenetic characters will perhaps approach 

 those of the latter, but the phylogenetic movement may be in quite 

 another direction. 



Another ontogenetic species is the little char or trout, Salvelinus 

 tudes Cope, from Unalaska. In Captain's Harbor, Unalaska, the 

 Dolly Varden trout, Salvelinus malma, swarms in myriads, in fresh 

 and salt water alike, reaching in the sea a weight of six to twelve 

 pounds. A little open brook, which drops into the harbor by an im- 

 passable waterfall, contains also an abundance of Dolly Varden trout, 

 mature at six inches and weighing but a few ounces. This is Sal- 

 velinus 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 phylogenetic characters, the two forms of trout are one 

 species. We have reason to believe that fry from the bay would grow 

 up as dwarfs in the brook, and that the fry from the brook would be 

 gray giants if developed in the sea. 



But it is also supposable that in the complete isolation of the 

 brook fishes, with free interbreeding, there would be some sort of 

 phylogenetic bond. There may be a genuine subspecies, tudes, char- 

 acterized not by small size, slender form and bright colors, but by 

 other traits, which no one has found because no one has looked deeply 

 enough. 



In no group of vertebrates are the life characters more plastic than 

 among the trout. The birds have traits far more definitely fixed. Yet 

 differences in external conditions must produce certain results. I 

 should not venture to suggest that the dusky woodpeckers or chickadees 

 of the rainy forests of the northeast and northwest are purely onto- 

 genetic species or that they should be erased from the systematic lists. 

 But it will be a great advance in ornithology when we know what they 

 really are and when we understand the real nature of the small-bodied, 

 large-billed, southern races of other species of birds. It would be 

 worth while to know if these are really ontogenetic purely, or if they 

 are phylogenetic through ' progressive heredity,' the inheritance of 

 acquired characters, such as the direct effects of climate or as the 

 reaction from climatic influences. Or again, may there be a real 

 phylogenetic bond through geographical segregation, its evidences ob- 

 scured by the more conspicuous traits induced by like experiences ? Or 

 are there other influences still more subtle involved in the formation of 

 isohumic or isothermic subspecies? 



Functional Variations 



Functional variations are variations produced in the individual by 

 the use or disuse of organs. They are most marked in the most active 



