ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07821.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

摘要:

SUMMARY.It must be evident, to those who have read the earlier sections of this paper, that the question of the systematic position of the Colies is not one that can be easily or over‐confidently answered. But all the available evidence tends to shew that the nearest allies of this group are theCypseli; though, as will be seen, in many points the two groups do not agree very closely, and this more especially with regard to the skeleton.In the matter of their pterylosis theColliandCypselishew a remarkable and significant likeness, and this is most apparent, perhaps, when nestlings are compared. In the present paper these comparisons have been made betweenColius affinisandCypselus apus.In both groups thepteryla capitisis interrupted by an apterion; but while this apterion inColiusis of considerable size, and extends outwards to join the ocular areabehindthe eye, inCypselus apus(for example) it is very narrow and joins the ocular area infrontof the eye. Moreover, the feathers are arranged differently in the two types. InCypselus apusthere is a sharply defined, tongue‐shaped, frontal area, wherein the feathers are closely set, contrasting with the more sparsely feathered parietal area.In both theColiiandCypselithe spinal tract is interrupted by a long narrow apterion, while the pterylse are of unusual width throughout the body, thus reducing the apteria to a minimum. The difference in the form of the wing is entirely due to the difference in habit between the two groups, the one being of a sedentary habit and flying little, the other extremely active and depending for sustenance on insects caught in mid‐air.The myology of the two groups, when compared in this connexion, is less convincing. A comparison of the wingmuscles, for example, reveals nothing, so far as the question of relationship between the two groups is concerned; inasmuch as theCypselihave undergone very profound modifications with regard to the wing–a degree of extreme specialization which has obliterated all the more normal, more primitive characters.In the muscles of the thigh theCypselishew no less extreme modifications, or, as Dr. Chalmers Mitchell has it, apocentricity.The plantar tendons of these two groups appear, at first‐sight, to be no more helpful in this connexion, inasmuch as, so far as the matter has been investigated, three very distinct combinations of these tendons have been brought to light, combinations represented respectively by the Colies, Swifts, and Humming‐birds. If correctly interpreted they shew, however, that they must be regarded as so many modifications of a common and primitive plan, wherein theflexor longus hallucissplit up to serve each of the four toes, while theflexor perforans digitorumwas restricted in its ramifications to digits II., III., IV., the two tendons being unconnected by a vinculum. Such an arrangement, among living birds, has been found, so far, only inHeliornis,an aberrant Gruine bird. It would be beside the purpose of the present paper to enter into a discussion of the evolution of all the known types of plantar tendons, but we may gain a most instructive insight into the matter by the tendons in the Colies and the forms therewith associated–the Swifts and Humming‐birds.Curiously enough, the Humming‐birds approach nearest to this primitive type, though even there a considerable degree of specialization has continued to mask the evidence of the earlier co

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07822.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07823.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07824.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07825.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07826.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07827.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07828.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1907.tb07829.x

出版商:Blackwell Publishing Ltd    

年代:1907

数据来源: WILEY