306 Prof.H. O. Seeley — On Vogt's VieiD of the AraJmopteryx. 



The second part of the paper is entirely theoretical ; and is an 

 argument designed to sliow the considerations which weigh with the 

 author in his interpretation of Arch(eoptertjx. He first shows that 

 the vertical position does not imply flight, then that flight is inde- 

 pendent of an upright position, next that adaptation to flight is seen 

 in the shoulder girdle and in the proportions of the bones ; flight is 

 then considered, first by means of a membrane as in Pterodactyles, 

 Flying-squirrels, and Bats, and secondly by means of feathers, so as 

 to show how the skeleton is modified in each case. He remarks 

 that the flight of the Arclifeopteryx may in some measure be com- 

 pared with that of Galeopithecus among mammals, but that it is 

 a step further forward in the march of adaptation. It is affirmed 

 "that no naturalist on being shown the skeleton of Jrcho'opteryx, 

 alone and without the feathers, could suspect that this animal had 

 been in its lifetime furnished with wings." For it is observed that 

 if " we could for a moment remove all the feathers we should have 

 before our eyes the tridactyl manus of a Eeptile. And yet it is 

 added, " The number of digits and the single carpal depart from the 

 normal structure of Eeptiles. The digits, without doubt, are 

 altogether of the most decidedly reptilian conformation ; but they 

 are reduced to the normal number possessed by Birds, and the 

 middle digit is the longest of the three." This is Vogt's view. At 

 the beginning of the argument the animal is re})tilian ; at the end the 

 bird is becoming evolved. I have a suspicion that the skeleton is 

 far from suggesting that the animal was destitute of wings ; for the 

 only characters which could promote such a doubt are the unanchy- 

 losed condition of the metacarpal bones and the claws. The former 

 point is a difference from birds, but in my view much less important 

 than a difference of osteological plan would have been, and no more 

 important than the persistence of separate epiphyses, or cranial 

 sutures. That the skeleton in existing birds happened to have its 

 distinctive structure of the manus is, I suppose, an accident conse- 

 quent upon the way in which the wing feathers came to be developed 

 so as to affect the vascular system and ossification. I believe 

 it will be found convenient, on the hypothesis that the feathers 

 are the main cause of specialization in the bird, to define an animal 

 as being a bird so soon as it possesses the avian plumage, because 

 the vital organization could experience no important change from 

 this cause which might not as well have been developed by wings 

 of the Ornithosaurian type. 



The author then proceeds to discuss the affinities of Archceopteryx, 

 remarking that the Cretaceous birds, so well described by Professor 

 Marsh, form, a further indication of the course of Avian evolution, 

 since, "except some secondary points in the structure of their 

 vertebrae, their only Eeptilian character is the presence of teeth in 

 both their jaws." The gap, however, between the Odontornithes 

 and Arch^opteryx is confessedly very great. He is unable to unite 

 Compsognathus with ArchcBopteryx, as Prof. Gegenbaur has done, 

 or to see in it an ancestor of the bird, because it has no trace of 

 feathers, has very short fore feet, and hind feet formed like those 

 of reptiles. An equal difficulty is felt in regarding the Dinosauria 



