1895.] 427 [Grote. 



guide, no approximate uniformity is attainable in our systems of nomen- 

 clature. As a rule, in selecting generic characters, more stress should be 

 laid on those not prominently affected by special needs in the struggle for 

 existence. Such are more liable to modification, while each modification 

 or variation, working in a given direction and correlated with habit, is 

 temporarily fixed by inheritance. It must be to the working of this law 

 distinctively that species exist. Variation may be called forth by natural 

 selection, or by d3fnamic forces, but only heritable characters can persist. 

 Reversion, as I have said elsewhere, is only inheritance at a distance. 

 When inheritance has rendered permanent for a time a new modification, 

 it does not eradicate all trace of form^ equally and relatively permanent 

 states in the past history of the organism. Given conditions in some way 

 resembling the former, which produced an older modification, then the 

 tendency is to bring the older modification to the surface. It follows 

 from the observations already made, that all the cells are essentially re- 

 cipient. As long, then, as genera are not based upon characters of phy- 

 logeny, they will remain matters of opinion, or again of convenience. 



In the Hypeninaj there is a tendency in the males to develop extraor- 

 dinary secondary characters. These are not confined to a single organ, 

 but affect the appendages in general. These structures are partly useful 

 to the insect and adaptive and are rather of specific than generic valuiG. 

 For generic characters should clearly be chosen from those not favoring 

 the idea that they have arisen from a change of habit or from the tendencj' 

 to produce extraordinary structures in a given direction. The usual sex- 

 ual differences in the moths, pectinated and simple antennae, here extend 

 to other regions of the body ; none the less are they of similar morphologi- 

 cal importance. The antennae are modified in Zanclognatha, Chytolita, 

 Renia, Bleptina; the palpi in Palthis; the wings in Plethypena and Gabe- 

 rasa. But the most common and extraordinary variations are presented 

 in the strvicture of the front pair of legs. All these features have been 

 fully described in the late Revision by Mr. J, B. Smith for the American 

 species, and in calling attention to them, the object here is to suggest that 

 their value in uniting species under one genus may be overestimated. 

 Species which present similar ornaments to the anterior legs, but which 

 show other, apparently minor, because less striking differences, in other 

 parts of the body, should not be considered as congeneric of a necessity. 

 The tendency in the group to present exaggerated tuftings on the front 

 legs, or abortion of the front tarsi, may be exhibited along different im- 

 mediate or generic lines of descent. So, in Sisyrhypena, the peculiar 

 " wing form and color " are quite sufficient to authorize a different genus 

 from Litognatha. In my opinion the strange pattern of Pallachira might 

 allow a separate generic title. 



Among the forms which have been incorrectly referred to the present 

 group is Hycteola revayana (undulana). Dr. Chapman writes me, that 

 the egg is very much the same as that of Pseudoips bicolorana. That is, 

 it is like an Acronycta egg, but flatter and with more numerous ribs. The 



