462 TROPICAL NATURE Ix 
shapes of the primary wing-feathers, in the relative length of 
the hind toe, or in habits of life, as in roosting and building 
on trees. But the above objection shows how completely 
the principle of selection has been misunderstood. It is not 
likely that characters selected by the caprice of man should 
resemble differences preserved under natural conditions, either 
from being of direct service to each species, or from standing 
in correlation with other modified and serviceable structures. 
Until man selects birds differing in the relative length of the 
wing-feathers or toes, etc., no sensible change in these parts 
should be expected. . . . With respect to the domestic races 
not roosting or building in trees, it is obvious that fanciers 
would never attend to or select such changes in habits.” 
Studies of Cultivated and Wild Plants 
Still more remarkable, perhaps, is the collection of facts 
afforded by plants, which can be so much more easily culti- 
vated and experimented upon than animals, while the general 
phenomena they present are strikingly accordant in the two 
kingdoms. As an example of the great mass of facts afforded 
by horticulture, he records that three hundred distinct varie- 
ties were produced, in the course of fifty years, from a single 
wild rose (Rosa spinosissima). We find in these volumes 
enormous collections of facts on bud-variation, or the occur- 
rence of changes in the flower or leaf-buds of full-grown 
plants, from which new varieties can be and often are pro- 
duced ; and, after a most full and interesting discussion of 
the cases, it is shown that some are probably due to reversion 
to an ancestral form, others to reversion to one parent when 
the plant has been derived from a cross, and others, again, to 
that spontaneous variability which seems to be the universal 
characteristic of all living organisms. 
Three very interesting chapters are then devoted to the 
subject of inheritance, and a host of strange and heretofore 
inexplicable facts are brought together, compared, and classi- 
fied, and shown to be in accordance with a few general prin- 
ciples. Then follow five chapters on crossing and hybridism, 
perhaps the most important in the whole work, since they 
afford the clue to so much of the varied structure and com- 
plex relations of animals and plants. Notwithstanding the 
