FACTS IN EMBEYOLOGY. 229 



much for a connection of some kind between the lower and 

 higher, or extinct and living, species of animals of the same 

 families, and pretty clearly show that the higher and existing 

 species are, in many instances, the result of an extension of the 

 identical gestative process which, in its lower stages, was exem- 

 plified in the ancient species. Such being the existing evidence 

 of a connection between ancient and modern species of the 

 same families and genera, and that the modern species exist, 

 at least as a progressed sequence of the principles involved in 

 the ancient, we will now quote from the same author some 

 further illustrations of the analogies and connections existing 

 between the different and successively created divisions of the 

 Animal Kingdom as a whole, with man at its head : 



* The unity of structure in vertebrated animals," says he, 

 " has been understood, and well understood, long before Em- 

 bryology had added any thing to show how deep this unity of 

 plan was impressed on that type. By the investigations of 

 Comparative Anatomy, it had been ascertained that the external 

 differences which characterize the class of Fishes, that of Rep- 

 tiles, that of Birds, and that of Mammalia, were only modifi 

 cations of one and the same structure that the head of Fishes, 

 for example, though apparently so different from that of Man, 

 was made up of the same bones, arranged in the same man- 

 ner, only sub-divided into more distinct points of ossifica- 

 tion, with modified proportions, most of them remaining 

 movable for life, but, after all, arranged upon the same uniform 

 plan." 



In a previous paragraph, the same author says : " It was in 

 Physiology, a great discovery, when it was ascertained that 

 all Vertebrata, that Fishes, as well as Reptiles, as well * as 

 Birds, as well as Mammalia, arose from eggs, which have one 

 and the same uniform structure in the beginning, and proceed 



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