DEVELOPMENT. 211 
known and respectable members of society.” Thus, cer- 
tain Butterflies on the Amazons have such a strong odor 
that the Birds let them alone; and butterflies of another 
family in the same region have been found disguising 
themselves for protection by assuming the same form and 
color of wing. So we have bee-like Moths, beetle -like 
Crickets, wasp-like Flies, and ant-like Spiders; harmless 
and venomous Snakes copying each other, and Orioles de- 
parting from their usual gay coloring to imitate the plum- 
age, flight, and voice of quite another style of Birds. The 
species which are imitated are much more abundant than 
those which mimic them. There is also a general har- 
mony between the colors of an animal and those of its 
habitation. We have the white Polar Bear, the sand-col- 
ored Camel, and the dusky Twilight-moths. There are 
Birds and Reptiles so tinted and mottled as exactly to 
match the rock, or ground, or bark of a tree they fre- 
quent; and there are Insects rightly named “ Walking- 
sticks” and “ Walking-leaves.” These coincidences are 
not always accidental, but often intentional on the part 
of nature, for the benefit of the imitating species. Gen- 
erally, they wear the livery of those they live on, or ape 
the forms more favored than themselves. _ 
5. Homology, Analogy, and Correlation. 
The tendency to repetition in the development of ani- 
mals leads to some remarkable affinities. Parts or organs, 
having the like origin and development, and therefore the 
same essential structure, whatever their form or function, 
are said to be homologous; while parts or organs ana- 
tomically different, but corresponding in use, are called 
analogous. 
The following are examples of homology: the arms 
and legs of Man; the upper and lower set of teeth ; 
the parts of the vertebral column, however moditied ; the 
