TRANSITION TO THE AMPHIBIANS. 



259 



versed in the history of development, has pointed out 

 to me, — supporting his remark on the comparison of the 

 respiratory organs of the Marsipobranchii with those 

 of the amphibians, — it is possible that frogs and sala- 

 manders may be directly descended from beings closel} 

 analogous to the division of the Marsipobranchii termed 

 Myxine. It is to be hoped that this highly interesting 

 observation itiay soon be made public. We gather from 

 the general Ontogenesis of the amphibians, that the tailed 

 forms are the most ancient. This is also the case with 

 the oldest amphibian-like animals, the Labyrinthodonts. 

 From their remains (Archegosaurus and others), chiefly 

 contained in the Carboniferous formation, we have learnt 

 that they had incomplete limbs or none, that their ven- 

 tral side was partially provided with bony plates, the 

 vertebral column fish-like, and that their skull, with sorne 

 of the characters of the present amphibians, combined 

 others which remind us partly of certain bony Ganoids, 

 and partly of the reptiles which subsequently appeared. 

 Now if in the singularly elongated snake-like Coecilia, 

 which is however without tail or limbs, some peculiarities 

 of the skull of the Labyrinthodont appear again, we must 

 own our utter ignorance as to the actual progenitors of 

 this, as well as of the two other living orders of the 

 Coeciha and the Batrachians. Here, therefore, we are, 

 as we have said, thrown entirely on the evolutionary 

 history of the individual. By what right we may 

 frame a picture with great probability approaching the 

 truth, the reader may have gathered from our previous 

 chapters. 



Among the tailed amphibians, it is not only in 

 Ontogenesis that we see the passage from gill to lung- 



