ANIMAL KINGDOM. 



compose the sjjine. Tlie nerves communicate with tins me-' 

 dullary trunk by holes in the vertebras and skull, and there', 

 appear all to unite in a double medullary band, which, after 

 having crossed its filaments, spreads itself in order to forn^ 

 the different tubercles of the brain, and to terminate in the 

 two medullary hemispheres of which the volume generally 

 corresponds with the extent of intelligence!. ' 



As the vertebrated spine is the distinguishing niaiTC '6T 

 these animals, it is evident that the imperfection of this cha- 

 racter will always point out the particular species by which 

 weare to leave the group. Thebones,aswe have seen in the 

 Cephalopoda and Reptiles, were at first represented by carti* 

 lages; we naturally look therefore for those other vertebrated 

 animals which have their skeleton particularly cartilaginous. 

 The Chondropterygian fishes have the calcareous matter 

 deposited in their skeleton by small grains and not by fibres 

 or filaments . The articulations gradually disappear in these 

 animals, and hi the Lampreys we find the spine composed 

 of one solid cartilage upon which the last trace of articula- 

 tion appears as wrinkles. Fins and every other vestige of 

 limbs or members are here at last totally lost. An efori- 

 gated body is terminated by a fleshy circular Or semicir- 

 cular lip, and the cartilaginous ring which supports this 

 Bp results from the palatines and mandibles being soldered 

 together. The branchias, instead of being formed of la- 

 minae as in other fish, have the appearance of purses' or 

 bags, resulting from the union of the face of one pair 

 with the opposite faces of its neighbour. We are arrived, 

 in fine, at animals, such as the genus Ammoc&tus of Du- 

 meril, where the skeleton is soft and membranaceous, or 

 as the genus Gastrobranchus or Myxine, where no trace 

 of the eye exists, where the maxillary ring itself becomes 



