i64 Journal of Comparative Neurology. 



[Blattd) or entirely absent {Forficida, Aanditim, etc.) ; while in 

 the Hymenoptera the calyx is folded upwards so as to give 

 room for many more neural elements and connections. 



If one considers the little that has thus far been made known 

 by means of the bichromate of silver and the methylen-blue 

 methods concerning the cerebral nerve fibers in other inverte- 

 brates, one finds that sensory stimuli are transferred to a num- 

 ber of irregular cells or fibers distinguished roughly by the term 

 association fibers and from these transferred to motor or other 

 , fibers bearing efferent neural impulses. And from such a com- 

 parison it appears that in the groups of insects certain of these 

 association fibers have gradually been set apart from the rest so 

 as to render it possible for an entering stimulus to become an 

 efferent impulse by taking a direct or an indirect course. In 

 the former case the course is to be compared with the course of a 

 stimulus producing reflex action in man. Later on it will be 

 seen that the present assumption of the existence of fibers per- 

 mitting such a course is fairly well founded. Thus a sensory 

 impulse from an optic lobe or from an antenna may reach the 

 fibers going to the mouth parts through possibly but one asso- 

 ciation fiber. 



In the other case it may take a special or somewhat indi- 

 rect course to and through the fibers of the cells of the mush- 

 room bodies and from them reach the efferent fibers through 

 the processes of one or more association cells. From those facts 

 it seems far within the bounds of reason to suppose that the 

 nerve cells of the mushroom bodies rendered so prominent by 

 their specialization of form and position are the elements that 

 control or produce actions that one distinguishes by the term 

 intelligent. 



An analysis of these actions is needed, but that is beyond 

 the limits of this p.iper. Suffice it to point out that the exper- 

 iments of Binet ( 94) and others show that when the connections 

 between the dorso- and ventro-cerebron are destroyed the phe- 

 nomena afterwards observed are similar to those seen in a 

 pigeon or mammal when its cerebral hemispheres are removed. 

 One difference is notable, namely, that the operation of eating 



