Journal of Comparativk Nkukology. 



b. Area olfactoria . . . . . ,41 



c. Nucleus thaeniae . . • . . . 41 



d. Lobus olfactorius . . . . .42 

 IV'. Theoretical CoNsiuEKArioNs .... 44 



.-/. The Sensory Systems . . . . . . ^4 



a. The sense organs. Pit organ';. End-buds . 44 



b. The cranial nerves ..... 47 



1. The vagus group . • . . .47 



2. The VII-VTII complex ... 49 



3. The trigeminus . . . . .50 

 Summary ..... :;0 



c. The sensory centers . . . . -55 



1. Cutaneous (somatic) centers ... 53 



2. Fasciculus communis . . .64 



B. Mid, ' Tiveen, aitd Fore Brahi .... 66 



a. Lobus olfactorius . . . . .69 



b. Fore brain ...... 70 



c. 'Tween brain . . . . . .72 



d. Tectum ...... 72 



C. Printrth't' Characters in tlw Prtronivziui Brain . . 73 

 V. Summary ok Results ..... 76 



List ok papers cited ...... So 



Description ok i'ioi'res ..... S2 



I. Intro DUCT I O.N. 



The species used for this investii:,ration is the common 

 brook lamprey, Lampetra ivilderi. GoLoi preparations were 

 made in 1897 and others in 1898 for the purpose of making 

 some comparisons with the brain of Acipenser. So many points 

 of interest were noted that it was decided to lay the prepara- 

 tions aside for more complete study later. The paper deals 

 with the minute structure of the various brain centers, the fiber 

 tracts and the central relations of the cranial nerves. It is a 

 contribution to our knowledge of the mechanism of sentient 

 life in lower vertebrates, as a foundation for the study of the 

 localization of central nervous functions and the physiological 

 (psychological) significance of the various regions of the higher 

 vertebrate brain. An attempt lias been made in the study of 

 the brain of the sturgeon and of the lamprey to seek out the 

 earliest or most primitive form of the well khown brain centers 

 of higher forms, to stud\- them with reference to their possible 



