CHARACTERS OP THE CLASSES OF VERTEBRATE ANIMALS. 



13 



Procreation is rarely attended with a coitus or intromission, the 

 requisite accessory organs being wanting in the majority of the class : 

 and the product still more rarely receives, after exclusion, any pa- 

 rental attention or care. 



<s 1 

 b 



9-\ 



Blood-discs, each magnified 300 diameters linear, "a, Man ; h. Musk-deer ; c. Goose ; d. Crocodile ; 

 e. Frog ; /, Siren ; g. Cod-fish ; h. Skate. 



In many respects Fishes typify the embryonic stages of develop- 

 ment of the higher animals : they were the first created Myelence- 

 phala ; and, through a series of vast geological periods, as the Silurian, 

 Devonian, and, perhaps, the Carboniferous, the sole representatives 

 of the Vertebrated sub-kingdom in this planet. 



The second class of Vertebrated animals, called Reptilia, l)y no 

 means presents so uniform a type as that of Fishes. Reptiles have 

 more varied spheres of action. Some retain the form and breathe 

 the element of fishes, living and moving in water during the whole or 

 a part of their existence. The transition, indeed, from Fishes to 

 these lowest Amphibian or Batrachian forms is so close and gra- 

 dual, that whilst some true Reptiles* have passed for Fishes, the 

 higher Fishes f have been classed with Amphibia, and even at the 

 present day, a true Fish — the Protopterus or Lepidosiren — has been 

 described, and by some natui'alists is still regarded, as a Reptile. 

 But no Reptile has dorsal parapophyses or the scapular arch articu- 

 lated to the occiput, and every Reptile has two auricles to the heart, 

 and the nasal canal communicating with the mouth. The Tortoises 

 {Chelonia) and Lizards (Sauria) have locomotive members adapted 

 for progression on dry land ; but they can only raise the body a little 

 way, if at all, above the ground, and creep rather than walk : the 

 Serpents (Ophidia) have no visible members, but move by the 

 reaction of the entire trunk upon the ground, and so drag their 

 belly through the dust of the earth: whence the name " Beptilia" 

 (repo, to creep), given to this class of Vertebrate animals. 



* Larvae of liana Paradoxa, called Frog-fish. 



\ Sharks and Rays, called " Amphibia nantcs " by Linnaeus. 



