the term Homology in modern Zoology. 41 
found very useful to employ it, and it could not be used with 
any accuracy in place of homoplasy. Any two organs having 
the same function are analogous, whether closely resembling 
each other in their structure and relation to other parts or not; 
and it is well to retain the word in that wide sense. Homo- 
plasy includes all cases of close resemblance of form which are 
not traceable to homogeny, all deta?/s of agreement not homo- 
genous, in structures which are broadly homogenous, as well 
as in structures having no genetic affinity. 
There may be other less direct causes at work in pro- 
ducing homoplasy besides an agreement in environment or 
external evoking conditions; such a cause is indicated in the 
remarkable cases grouped by Mr. Darwin as correlations of 
. growth, and for which the term homotrophy may perhaps be 
rae 
med and slightly modified in various branches of the race. 
though their homology has not been maintained for man 
years. "The beak of a bird is to a considerable extent homo- 
plastic with the beak of a chelonian, the dorsal and caudal 
fins of a cetacean with those of some fish, the sete of Acan- 
