Edinger, Comparative Psychology. 449 



how far does observation of the behavior of the animals accord 

 with the fact that a new mechanism has been added to the palaeen- 

 cephalon ? The cortex of serpents consists of several layers of 

 cells which are manifoldly connected by means of countless fibers. 

 Judging from our knowledge of mammals, we should naturally 

 take the view that such a mechanism renders possible the holding 

 back of an impression and the associating of one impression with 

 another. The tracts which lead to this association mechanism 

 come from the center for the olfactory and oral senses. Others, 

 such as tracts from the center for the optic nerve, have not yet 

 been found in the animals which have been studied. This is in 

 accord with the fact that the reptiles recognize prey optically 

 usually only as some definite combination, such as the mov- 

 ing mouse, the moving frog. The optic impression of the resting 

 mouse does not by itself suffice to induce seizing. But one readily 

 sees that these animals use the olfactory and oral senses very differ- 

 ently from the amphibians. A serpent, by touching with the tongue, 

 determines whether it has an animal of one kind or of another. 

 It marks where a food animal has been resting and finds it by 

 following it to its lair. By testing the surface of the water with 

 the tongue the ringed-snake determines if there are fish in the 

 water. The oral sense is very much used. Occasionally the ani- 

 mals try to devour pieces of wood upon which prey has rested and 

 left its odor, but after touching they turn away. Zamenis, by touch- 

 ing, selects a pigeon egg from amongst a number of turtle eggs 

 of the same size. The hungry serpent is restless, it makes shght 

 movements, touches the ground, it seeks food — something which 

 the frog is never observed to do. 



In another respect reptiles differ from those animals which do 

 not possess a cortex. If the latter fail to obtain the prey which 

 has stimulated them to eat, they remain quiet until a new stimulus 

 appears. Not so with reptiles. Serpents, once stimulated by a 

 jumping frog or a running mouse, follow their prey at least for a 

 time and, guided by the olfactory and oral senses, they are able 

 amongst a number of holes to find that particular one into which 

 the prey has crept. Finally, there first appears in reptiles some- 

 thing which indicates that they occasionally foresee what may 

 follow from a certain experience. Many lizards and serpents 

 assume an attitude of defense when danger threatens. They 

 direct the head toward the enemy, raise the forward part of the 



