HUXLEY AND HIS WORK. 773 



indeed many. The question, then, was How far can this gap be filled 

 up by a reference to the records of the life of past ages ? 



"The question resolves itself into two: 



" (1) Are any fossil birds more reptilian than any of those now living? 



"(2) Are any fossil reptiles more bird-like than living reptiles'? 



Both of these questions Huxley found "must be answered in the 

 affirmative." 



The remains of Archaeopteryx found in the "lithographic slate of 

 Solenhofen" furnished a bird with decided reptilian characters — so 

 prominent, indeed, that some of the paleontologists of the period 

 claimed that the animal was a reptile rather than a bird. 



The remains of various Dinosaurians of Mesozoic times yielded rep- 

 tiles with characteristics manifest only among the birds of the present 

 epoch. Such characteristics were especially exemplified in details of 

 structure of the hind limbs. One of the Dinosaurians — Compsogna- 

 thus — was so much like a bird in the legs that "it is impossible to 

 doubt that it hopped or walked, in an erect or semierect position, after 

 the manner of a bird, to which its long neck, slight head, and small 

 anterior limbs must have given it an extraordinary resemblance." 



From the vantage ground of the present, with its increased stores, 

 we may justify Huxley's "hope" that he had redeemed his "promise to 

 show that in past times birds more like reptiles than any now living 

 and reptiles more like birds than any now living did really exist." 

 There is now even a tendency to regard the differences remaining 

 between the birds and reptiles as of less than class value, and to com- 

 bine both groups in one and the same class — Sauropsida. The first to 

 propose such a union was Professor Cope, who had even to some extent 

 anticipated Huxley in the recognition of the similarity between the 

 Dinosaurians and birds. The fact that two such men independently 

 arrived at similar conclusions is significant as evidence for their truth. 

 But there is danger of pushing a truth to the extreme of itself deceiv- 

 ing. There is still a great gap between any known reptile and any 

 known bird. Huxley concluded with the caution that, "as we possess 

 hardly any knowledge of the terrestrial reptiles of [the Triassic] period, 

 it may be regarded as certain that we have no knowledge of the ani- 

 mals which linked reptiles and birds together historically and genetic- 

 ally, and that the Dinosauria, with Compsognathus, ArchceopteryXj and 

 the struthious birds, only help us to form a reasonable conception of 

 what these intermediate forms may have been." This cautious state- 

 ment is as apt for the present time as that in which it was expressed." 



VIII. 



One of the most persistent prejudices that has influenced the progress 

 of zoological taxonomy has been (perhaps still is) a belief in the import- 

 ance of superficial adaptation of structure for life in the water contra- 

 distinguished from life on the land. This prejudice was long impressed 



