REPTILES 



203 



large optic lobes, much like those of a Bird (see p. 1 50), but placed 

 side by side on the upper side of the brain instead of being 

 separated from one another. Lastly comes the medulla oblongata, 

 which passes gradually back into the spinal cord, and exhibits 

 on its upper side, just behind the optic lobes, a small smooth 

 lobe which corresponds to the complicated cerebellum found in a 

 Mammal or Bird (see pp. 52 and 150). A side view of the brain 

 shows clearly a sharp downward bend (cranial flexure) in the 

 region of the medulla oblongata. 



The same sense organs are present as in a bird, though there 

 are many differences in detail; and it may be particularly men- 

 tioned that the complex bag or membranous labyrinth (see p. 150), 

 which is imbedded in the side wall of the skull and constitutes the 

 inner ear, is rather less complex. 



In dealing with the skull it was mentioned that there is a small 

 hole, the parietal foramen, in the roof of the brain-case. This hole 

 is occupied by a rounded structure, which in some Lizards has 

 clearly the structure of an eye, so much so that it is usually called 

 the pineal eye. It is connected with a sort of stalk which runs 

 upwards from that part of the brain-axis of which the cerebral 

 hemispheres are outgrowths. Even in Lizards this unpaired eye 

 is more or less degenerate, and it is only represented in most of 

 the Vertebrates by the stalk just mentioned, to which the name 

 of "pineal body" is usually given. Even in the human brain a 

 pineal body can be distinguished, and the fact that the philosopher 

 Descartes regarded it as the seat of the soul has invested it with 

 a certain curious interest. It is clearly to be regarded as one of 

 those " vestigial organs" or "vestiges" which are of common 

 occurrence in the animal body, and represent the dwindling 

 remains of structures which were of importance in ancestral forms. 



Development. The Sand- Lizard lays eggs much like those of 

 a bird, but with softer shells. 



Classification of Reptiles. Leaving the numerous extinct 

 groups out of consideration, as these will be dealt with elsewhere, 

 Reptiles may be divided into five orders, as follows: 



1. Crocodilia: Crocodiles, Alligators, &c. 



2. Chelonia: Turtles and Tortoises. 



3. Lacertilia : Lizards. 



4. Ophidia: Snakes. 



5. Rhynchocephala : Hatteria, a lizard-like New Zealand form. 



