44^ 'Journal of Comparative Neurology and Psychology. 



and feathers, providing the angler rightly imitates the hopping 

 movement. The entire art of anghng, concerning which we possess 

 large volumes, depends upon knowledge of the proper stimulus 

 and upon the excluding of disturbing stimuli, such for example as 

 a thick fish-hne. Frogs may be caught by means of heath-berries 

 dangled before them on a string. Even the frog has a rudimentary 

 neencephalon, but so far as my observations go, it plays no part 

 in the obtaining of food. It still eats palaeencephaHcally. No 

 matter how hungry a frog may be, it seizes the earthworm only 

 when it crawls, or catches the fly only when it makes some move- 

 ment. One may lay a worm on the frog's snout or may in any 

 way bring the two in contact, but eating does not result. The 

 worm acts as a stimulus only when crawling, otherwise it is not 

 recognized. One can very clearly observe how the entire operation 

 of eating results from the addition of very definite reflexes. The 

 crawling worm first induces, by way of the optic nerve, possibly 

 also by way of the acoustic nerve, a turning of the head; if it crawls 

 further a new stimulus is added, and then the body is turned, the 

 head sinks and, if the stimulation continues, the seizing results. If, 

 as frequently happens, the animal misses the prey it does not 

 immediately strike at it again. The worm must crawl further 

 and the entire series of reflexes must be repeated. If the worm 

 stops crawHng, the series is at that moment interrupted. Upon 

 the other hand, an object which is not eatable gives rise to the 

 seizing act provided that the same stimuli proceed from it as 

 from the worm. Hanau saw a toad follow and repeatedly snap 

 at a blind-worm's tail for hours. 



The sense stimuli which lead reptiles to the obtaining of food 

 are not materially difi^erent from those just described. Most ser- 

 pents, all hzards, and the carnivorous turtles appear not to see 

 motionless prey. However, they do not rush recklessly at moving 

 prey as does the frog at the heathberry, but they orient themselves 

 with respect to their food by snifl&ng or by touching with the 

 tongue. In some cases the stimulus is received through the sense 

 of hearing. But the serpents appear not to use this sense, for a 

 very hungry animal does not change its attitude when a mouse 

 squeaks or a bird calls. 



What, then, are the diff'erences in behavior which depend upon 

 the presence of the cortex in serpents ? Is it possible from the 

 structure of the cortex to formulate problems for observation, and 



