VERTEBRAL COLUMN AND ITS APPENDAGES. 89 



animals might be thought to be scarcely entitled to a place in 

 the Vertebrated series ; but they agree with Vertebrata in other 

 points of their conformation ; and the disappearance of even this 

 most distinctive character of the group, in its lowest forms, is 

 exactly what we should anticipate, on the principles formerly 

 stated ( 35). 



67. The vertebral column terminates at its upper or anterior 

 extremity, in the cranium or skull ; which is a large bony struc- 

 ture, formed of several pieces, closely united together, and 

 adapted to protect the brain, which it completely incloses, as 

 well as to afford a secure lodgment for the organs of special 

 sense, the eyes, nose, tongue, and ears. These organs, with 

 very few exceptions (and these principally relating to the eyes), 

 are all present in every Vertebrated animal ; which is not the 

 case in regard to the greater portion of the Invertebrata. At 

 the opposite end, the vertebral column is usually contracted into 

 a tail ; which is composed, like the part that gives support to the 

 trunk, of vertebras jointed together ; but which is not penetrated 

 by the spinal cord. The tail is developed in various degrees in 

 different animals ; least in Man, and in the Apes which approach 

 nearest to him, although even they have a rudiment of it ; and 

 most in Serpents and Fishes, in which the tail is the continuation 

 of the body. It has to serve a great variety of purposes ; and is 

 often an organ of the greatest importance in locomotion. A 

 curious antagonism may often be observed, between the develop- 

 ment of the cranium, and that of the tail. When the head is 

 large, as in Man, the tail is most commonly short and insignifi- 

 cant ; and when the tail is very large, the skull is usually small ; 

 but this does not invariably hold good. 



68. With the vertebral column are connected the ribs, which 

 are rarely absent; and also the bones of the extremities or 

 members, which are also occasionally wanting, and which are 

 developed in very varying degrees in different species. They are 

 altogether absent in the Serpent tribe, and also in a considerable 

 group of Fishes. In the Whale tribe, the posterior extremities 

 are absent ; and the anterior members, forming the paddles or 

 flappers, are small in comparison with the bulk of the body. 



