212 THE DESCENT OF MAN 



eral remarks. Every evolutionist will admit ttat tlie five 

 great vertebrate classes, namely, mammals, birds, reptiles, 

 amphibians, and fishes, are descended from some one proto- 

 type; for they have much in common, especially during 

 their embryonic state. As the class of fishes is the most 

 lowly organized, and appeared before the others, we may 

 conclude that all the members of the vertebrate kingdom 

 are derived from some fish-like animal. The belief that 

 animals so distinct as a monkey, an elephant, a humming- 

 bird, a snake, a frog, and a fish, etc., could all have sprung 

 from the same parents, will appear monstrous to those who 

 have not attended to the recent progress of natural his- 

 tory. For this belief implies the former existence of links 

 binding closely together all these forms, now so utterly 

 unlike. 



Kevertheless, it is certain that groups of animals have 

 existed, or do now exist, which serve to connect several of 

 the great vertebrate classes more or less closely. We have 

 seen that the Ornithorhynchus graduates toward reptiles: 

 and Prof. Huxley has discovered, and is confirmed by Mr. 

 Cope and others, that the Dinosaurians are in many impor- 

 tant characters intermediate between certain reptiles and 

 certain birds — the birds referred to being the ostrich-tribe 

 (itself evidently a widely diffused remnant of a larger group) 

 and the Archeopteryx, that strange Secondary bird, with a 

 long lizard-like tail. Again, according to Prof. Owen," the 

 Ichthyosaurians — great sea- lizards furnished with paddles 

 — present many af&nities with fishes, or rather, according 

 to Huxley, with amphibians: a class which, including in 

 its highest division frogs and toads, is plainly allied to 

 the Ganoid fishes. These latter fishes swarmed during the 



and s. 425); and with more especial reference to man in his "Natiirliche 

 Schopfungsgesohiohte," 1868. Prof. Huxley, in reviewing this latter work 

 ("The Academy," 1869, p. 42), says that he considers the phylum or lines of 

 descent of the Vertehrata to be admirably discussed by Hackel, although he 

 differs on some points. He expresses, also, his high estimate of the general 

 tenor and spirit of the whole work. 

 s» "Paleontology," 1860, p. 199. 



