THE BRAIN OF DIEMYCTYEUS VIRIDESCENS, 

 FROM LARVAE TO ADUET EIFE AND COMPARI- 

 SONS WITH THE BRAIN OF AMIA AND PETRO- 

 MYZON. 



SUSANNA PHELPS GAGE. 



The remarkable changes in habits, appearance, structure 

 and physiology which occur at two distinct crises in the life 

 history of Diemydylus viridescens, Raf.,"^ suggest the ques- 

 tion whether any corresponding changes in the brain occur at 

 these periods. Part I is a partial answer to this question. 



In order better to understand and honiologize certain parts 

 and regions of the diemyctylus-brain comparisons were made 

 with the brain of amia and of larval lampreys. The second 

 part of this article deals with these comparisons and the gen- 

 eral conclusions drawn from them. 



PART I. 



THE BRAIN OF DIEMYCTYLUS. 



In order to answer the question stated above the brain ol 

 diemyctylus has been studied in its various stages of develop- 

 ment (i6).t A few ova were prepared — effort was mainly di- 

 rected, however, to the stages following hatching ;— the very 

 young larvae (Fig. 12) ; older gilled larvae which are half 

 grown and ready to transform ; the gill less red form in three 

 stages of growth, and finally the adult viridescent form 

 (Fig. 11), male and female of various sizes. 



The investigation has been confined almost exclusively to 

 parts which in larger brains can be studied more or less per- 

 fectly by macroscopic sections and dissections. The purely 



* Spotted triton or newt, vermilion spotted salamander (16). 

 t The numbers in parenthesis refer to the bibliography. 



