IIO E VOL UTION OF TO-DA F. 



generalized characteristics that he considers it as 

 representing the common ancestor of all true mam- 

 malia, and has named the group the Condylarthra. 

 The number of connecting links uniting this animal 

 with the modern orders is very great. Still earlier 

 is found a series of fossils uniting birds and reptiles. 

 These classes, in their anatomy, show a close rela- 

 tionship, and they have been united in a surprising 

 manner by fossils. The world-renowned Arche- 

 opteryx and the remarkable Odontornithes, the 

 toothed birds of the American Cretaceous, are reptile- 

 like birds ; while the Composgnathus seems to be a 

 bird-like reptile. Indeed, so successful have been 

 the researches upon fossil vertebrates, that Cope, 

 who has studied the subject with great care, thinks 

 that they have " disclosed the ancestry of the mam- 

 mals, the birds, the reptiles, and the true fishes," 

 and he unhesitatingly gives a phylogenetic history 

 of the whole vertebrate sub-kingdom. Whether this 

 history, as given by Cope, be right or wrong, does 

 not, however, concern us ; the very fact that it is 

 possible to make such a history from the study of 

 fossils, shows what a great advance has been made 

 in the direction of finding links, since the matter 

 has been subject to careful investigation under the 

 inspiration of the " Origin of Species." 



It is hardly possible to exaggerate the importance 

 of this result. From the very first the absence of 

 these connecting species has been recognized as a 

 most serious obstacle for evolution. But, as year 

 by year goes by, fresh discoveries have been con- 

 tinually bringing to light instance after instance 



