318 CBITIQUES AND ADDRESSES. [xn. 



in this general view of the Phylogeny of the Vertebrata 

 is, that the " Protamphirhine" was possibly more ganoid 

 than shark-like. So far as our present information goes 

 the Ganoids are as old as the Sharks ; and it is very 

 interesting to observe that the remains of the oldest 

 Ganoids, Cephalaspis and Pteraspis, have as yet displayed 

 no trace of jaws. It is just possible that they may 

 connect the Monorhina with the Sturgeons among the 

 Ampliirhina. On the other hand, the Crossopterygian 

 Ganoids exhibit the closest connection with Lepidosiren, 

 and thereby with the Amphibia. It should not be 

 forgotten that the development of the Lampreys exhibits 

 curious points of resemblance with that of the Amphibia, 

 which are absent in the Sharks and Rays. Of the 

 development of the Ganoidei we have unfortunately- no 

 knowledge, but their brains and their reproductive organs 

 are more amphibian than are those of the Sharks. 



On the whole, I am disposed to think that the direct 

 stem of ascent from the Monorhina to the Amphibia is 

 formed by the Ganoids and the Mudfishes ; while the 

 Osseous fishes and the Sharks are branches in different 

 directions from this stem. 



What the Protamniota were like, I do not suppose 

 any one is in a position to say, but I cannot think that 

 the thoroughly Lacertian Protorosaurus had anything to 

 do with them. The reptiles which are most amphibian 

 in their characters, and therefore, probably, most nearly 

 approach the Protamniota, are the Ichlhyosauria and 

 the Chelonia. 



That the Didelphia were developed out of some 

 ornithodelphous form, as Professor Haeckel supposes, 

 seems to be unquestionable ; but the existing Opossums 

 and Kangaroos are certainly extremely modified and 

 remote from their ancestors the " Prodidelphia" of which 

 we have not, at present, the slightest knowledge. The 



