iv JouKNAL OF Comparative Neukolcjgy. 



of all these nerves, in addition to containing, in its proximal portion, 

 certain of their pre- and post-trematic elements." 



The discussion of the chorda tympani is important, not because 

 of the presentation of any additional facts tending to fix the homolo- 

 gies of this perplexing nerve ; but rather by reason of the discovery of 

 fresh difficulties in the way of current interpretations. Most recent 

 writers, who accept the gustatory or communis character of the chorda 

 tympani, hold that this nerve in the mammals is pre-spiracular, i. e., 

 it lies morphologically cephalad to the Eustachean tube. Allis finds 

 this open to question and reviews the facts among the fishes and am- 

 phibians in the light of the possibility of the post-spiracular position of 

 the chorda. "The subject clearly needs further investigation, and first 

 of all it is absolutely indispensable to know the definite relations of 

 the chorda of mammals to the spiracular cleft." 



But these matters are really of less morphological interest than the 

 discussion of the homologies of the ampullary organs, which forms the 

 point of departure and motive for the entire research In his intro- 

 ductory paragraph he writes, "I have long had a very decided impres- 

 sion, opposed to that of most workers on the subject, that these am- 

 pullary organs must be genetically related to the terminal buds of ga- 

 noids and teleosts, rather than to the pit organs of those fishes." Mr. 

 Allis admits at the start that he has wholly failed to find any positive 

 evidence for this view, but adds, '"Careful consideration of these obser- 

 vations has fully convinced me, though indirectly, that the ampullary 

 organs do represent the terminal buds of ganoids and teleosts, and not 

 the pit organs." 



This conclusion has far-reaching applications, not apparent on the 

 surface perhaps, to many of the major problems now at the fore in 

 neurological morphology, viz. to all those problems connected with the 

 systems of nerve components either in the periphery or in the centers 

 and with the functional subdivision of the brain into neurone systems 

 in general. It is therefore important that the indirect evidence upon 

 which it is based be examined in some detail, since, as stated, it is 

 "opposed to that of most workers on the subject." 



The ampullae of Lorenzini of elasmobranchs, it will be recalled, 

 are small sense organs lying at the bases of long unbranched tubes 

 which open freely on the surface of the skin. The openings of these 

 tubes are scattered widely and tolerably uniformly over the surface of 

 the he ad, but the sense organs at the bottoms of the tubes are clustered 

 in well defined groups and are innervated by nerves closely related to 

 those of the adjacent lateral line canals. Previous authors generally 



