196 Mr. A. R. Wallace on the Natural Arrangement of Birds. 



nion, the mass of the other Passeres intervening between them. 

 In the case of these two families, a mere outward resemblance 

 appears to have been universally mistaken for an affinity. A 

 similarity in size, in the prevalence of metallic colours, and in 

 the slenderness of a very variable bill, has been taken to over- 

 balance the most important structural differences. The universal 

 characteristics of the Hummers are, excessively long wings and 

 as excessively small feet, w^ith more or less united toes. They 

 take their food exclusively on the wing. Every motion is made 

 upon the wing. The feet are solely used as means of support, 

 never for locomotion. The Sun Birds and their allies, the Ccere- 

 bidcB of America, have on the other hand long legs and toes, 

 the hinder toe especially being very long and powerful ; they are 

 therefore as capable of hopping and perching as any of the most 

 highly developed Passeres. Their wings, too, are short and round, 

 quite incapable of any powerful flight, and their tail almost in- 

 variably short and even. Much stress has been laid upon the 

 similar form and structure of the tongue. But the extensile 

 tubular tongue only exists in some genera {Anthreptes, Arachno- 

 therd), while in others it is short, flat, and not extensible (Dic(jeum, 

 CinnyriSj Ccsrebida). There is therefore no general agreement 

 of structure to unite these groups, except the solitary and 

 trivial one of an elongate and slender bill. 



On similar principles, we believe the Conirostres and Denti- 

 rostres to be equally untenable and unnatural. They are pro- 

 fessedly founded on one character only, and not on general 

 structure ; and it is therefore not to be wondered at, that in their 

 attempts to pay some httle regard to natural affinities, while 

 forcing the genera and families into these divisions, no two natu- 

 ralists should be able to arrive at the same results. The asso- 

 ciation of the Hornbills with the Crows, the separation of the 

 Larks from the Wagtails, and the necessity for putting Denti- 

 rostral birds (Tanagers and Jays) in the Conirostral tribe, are 

 some of the inconsistent results of the system. 



The remaining groups, the Scansores and the Fissirostres, we 

 believe to be much more natural, and in fact to be the only ones 

 which can be distinctly separated from the Passeres, of which 

 they form an abnormal development. It is to the arrangement 

 of these two groups that we more particularly address our- 

 selves. 



The Fissirostres are those passerine birds whose feet are 

 adapted solely for a state of rest, — all motion being performed 

 by the wings. With very rare exceptions, they never move the 

 shortest distance by means of their feet, — a character which di- 

 stinguishes them at once from all other Passeres, which either 

 hop, climb, or walk almost incessantly. Such a peculiar (Economy 

 must evidently depend upon corresponding peculiarities of or- 



