248 Journal of Comparative Neurology and Psychology. 



tween the centers of the two systems, since it is by accident that 

 the taste fibers enters the visceral centers. 



(3). If the dorso-lateral placodes represent a part of the 

 neural plate area of ancestral vertebrates, may not the epi- 

 branchial placodes be an offshoot from that also ? This sug- 

 gestion would have a point if it were shown that the end buds 

 had their origin from the epibranchial placodes as the neuro- 

 masts have their origin from the dorso-lateral placodes. It 

 would be necessary to explain further the wide separation be- 

 tween the epibranchial placodes and the neural plate, and the 

 permanent relation of the nerves of these placodes, not to the 

 margin of the neural plate but to the column which lies mesial 

 (ventral) to the cutaneous area of the plate. 



(4). The following suggestion seems to the writer most in 

 accord with such facts as we have at present. The end buds 

 are recent organs, formed comparatively late in the phylogen}^ 

 They appeared first in the vicinity of the mouth and gill slits 

 where they would detect indications of food in the respiratory 

 water current. In this position relative to the vertebrate neo- 

 stoma they would supplement the impressions received from 

 the olfactory organ. The animals in which end buds first ap- 

 peared may be thought of as relatively inactive, so that the 

 respiratory current formed their chief source of information as to 

 the presence of food. They were distinguished from such 

 animals as Amphioxus which feed by means of cilia by the fact 

 that they captured larger kinds of food by muscular movements. 

 This would be accomplished at first by means of the visceral 

 muscles of the jaws and branchial skeleton alone, the food per- 

 haps being sucked in by a sudden increase of the respiratory 

 current. The innervation of the end buds was determined by 

 their function. It is evident that they could not be innervated 

 by the general cutaneous component. For, if cutaneous fibers 

 could receive and transmit impulses due to chemical stimuli 

 those impulses would be interpreted in the brain as tactile im- 

 pulses ; that is, they would give rise to reflex movements which 

 characteristically follow upon tactile impulses. In the present 

 case this would be useless or harmful to the animal. On the 



