262 ON THE CLASSES OF THE 



peet tliat the brain will be at first far from voluminous, and 

 that the medullary matter will by no means be very concen- 

 trated. In other words, we may be sure that instinct and 

 industry will be extremely low, while muscular irritability 

 and tenacity of life will, on the contrary, be very observable, 

 ia the animals which form the transition to the Vertebrata. 

 Thus it is then with the Chelonian reptiles, in which the 

 brain is remarkably disproportionate to the size of the ani- 

 mal, and, as was shown by the cruel experiments of Redi, 

 is little if at all necessary to the existence of life. The brain 

 of the tortoise seems to be of no further use to the animal 

 than as a passive sensorium to which impressions are com- 

 municated by the organs of sight, smell, and hearing : and 

 the removal of it is said to be attended with consequences 

 to the possessor hardly more important than the loss of 

 these senses. The Chelonian circulation is rather singu- 

 lar; so that it has been said that they seem to have two 

 hearts joining one another, one of which is formed by the 

 two auricles, and the other, though apparently consisting pf 

 only one cavity, yet containing two veinous and two arterial 

 ventricles. These four chambers communicate together, 

 so that the black blood which comes from the body into 

 the right auricle, and the red blood which enters the left 

 fi"om the lung, are here always more or less mixed. 



M. De Blainville has separated the Batracians* fix>m 

 the other reptiles, on the principle that these come 

 nearer to birds in their organization, and the former 

 nearer to fish. He has therefore called the Batracian reptiles 

 of Brogniart Ichthyoides, and the other reptiles Ortiithoidff. 

 This arrangement is excellent, because it is natural; but 



• The idea of this class is by no means new, as the propriety of its 

 formation was indicated by Latreille several years ago, and lately again in 

 the new edition of the Dictionndire cTHUtoire NaturelU, art. EntomoUgie. 



