324 TRANS. ST. LOUIS ACAD. SCIENCE. 



dae on the other so intimately connect them, that it becomes 

 almost a matter of opinion as to whether the former should be 

 considered butterflies, or the latter moths. Urania and other 

 abnormal genera* make the relationship of the two groups still 

 more perplexing. On antennal structure alone — whether we 

 consider the clubbed or non-clubbed tips according to Boisduval, 

 or the rigidity, direction, and length, which Mr. Grote deems of 

 greater importancef — two primary divisions cannot be based. If 

 we take the spring or spine on the hind-wings, which is so char- 

 acteristic of the Heterocera, we meet with the same difficulty ; 

 for a large number of moths do not possess it, while an accepted 

 Hesperian {Euschemon Raffiesice^yidicX.^ from New South Wales 

 is furnished with it. Nor is there anyone set of characters which 

 will serve as an infallible guide to distinguish moths from butter- 

 flies ; and the number of moths described as butterflies, and the 

 fact that Kirby considers the ^o^\\!\onoi Barb icornis^ Threnodes^ 

 Pseudopontia^ Rhipheus^ yEgiale, and Euschcmon^ included in 

 his "Synonymic Catalogue of Diurnal Lepidoptera" as doubtful 

 butterflies, gives sufficient proof of the truth of the statement. 

 Between all classificatory divisions, from variety to kingdom, the 

 separating lines we draw get more and more broken in pro- 

 portion as our knowledge of forms, past and present, increases. 

 Every step in advance toward a true conception of the relations 

 of animals brings the different groups closer together, until at last 

 we perceive an almost continuous chain. Even the older natu- 

 ralists had an appreciation of this fact. Linnaeus's noted dictum, 

 '"'■ Natura saltus non facit" implies it ; and Kirby and Spence 

 justly observe that " it appears to be the opinion of most modern 

 ph} siologists that the series of affinities in nature is a concatena- 

 tion or continuous series ; and that though an hiatus is here and 

 there observable, this has been caused either by the annihilation 

 of some original group or species * * * or that the objects 

 required to fill it up are still in existence but have not yet been 

 discovered." Modern naturalists find in this more or less gradual 

 blending their strongest argument in favor of community of de- 

 scent, and speculation as to the origin, or outcome rather, in the 

 near present or remote past, of existing forms, is naturally and 



* Westwood {Intr. ii. 359) figures Barbicornts Basalts, God. as an Erycinid butterfly 

 with tapering and ciliate antennae. 



t Proc. Amer. Assoc. Adv. Sci. xxii., B. 111. 



