116 Mr. St. George Mivart on the Use 
, 
ues. 
Tn the second place we have two kinds of homogeny :—one, 
such as the evolutionary homogeny between the tarsus of 
. are formed from “imaginal disks " cannot be said to be de- 
velopmentally homogenous with the legs of such Diptera as 
are not so formed. i : 
That developmental homogeny is important, can hardly be 
denied, seeing that the great argument for the homology of 
any two parts has been generally held to be the fact of their 
undergoing the same process of development. Now it is in- 
convenient not to be able to indicate both kinds of homogeny 
and homoplasy by a common term; and therefore I think it 
better to preserve the word * homology." : 
Thirdly, I think it better to regard homoplasy as a species 
under homology, because the affinity between homoplasts and 
homogens is so much greater than between homoplasts and 
analogues, even sometimes when the latter are to a certain 
* Of course I mean not directly homogenous ancestrally, i. e. indepen- 
dently originated in structures which may or may not be homogens of a 
more remote and general kind, 
