MODERN SYSTEMS. 299 



the Ganoids should be also separated from the ordinary 

 Fishes. This, however, cannot be decided until their 

 embryological development has been thoroughly investi- 

 gated, though I have already collected data which favour 

 this view of the case. Should this expectation be rea- 

 lized, the branch of Vertebrata would contain the follow- 

 ing classes : 



1st Class: Myzontes ; with two orders, Myxinoids 

 and Cyclostomes. 



2nd Class: Fishes proper; with two orders, Ctcnoids 

 and Cycloids. 1 



3rd Class : Ganoids ; with three orders, Coelacanths, 

 Acipenseroids, and Sauroids; and doubtful, the Siluroids, 

 Plectognaths, and Lophobranches. 2 



4th Class: Selachians; with three orders, Chimaerse, 

 Galeodes, and Batides. 



5th Class : Amphibians ; with three orders, Ccecilke, 

 Ichthyodi, and Anura. 



6th Class: Reptiles-, with four orders, Serpentes, Saurii, 

 Ehizodontes, and Testudinata. 



7th Class: Birds; with four orders, Natatores, Grallae, 

 Easores, and Insessores (including Scansores and Acci- 

 pitres.) 



8th Class: Mammalia; with three orders, Marsupialia, 

 Herbivora, and Carnivora. 3 



1 I am satisfied that this subdivi- lumns, as other fishes do ; but chiefly 



sion of the Fishes proper requires by an undulatory movement of their 



modifications ; but I fear it would vertical fins, resembling very much 



lead me too far, were I to discuss the mode of action of the vibratile 



here the reasons for the changes I membranes. In this they resemble 



propose to introduce into it. the young Lepidosteus; and I consi- 



a I have observed a very curious der this fact as a new argument in 

 and peculiar mode of locomotion in favour of their association with the 

 all the Lophobranches, Scleroderms true Ganoids. Comp. also the re- 

 am! Gymnodontes, which I have seen marks respecting the limits of the 

 alive. They do not progre.ss by the Ganoids, p. 242. 

 lateral motions of the vertebral co- 3 Since this chapter was written 



