MORPHOLOGY OF THE FOREBRAIN 415 



Our immediate problem, then, is the relations of the first recog- 

 nizable primordia of the cerebral cortex to the other elements of 

 the evaginated cerebral hemisphere and of all of these structures 

 to the more ancient tissues of the telencephalon medium and dien- 

 cephalon. 



My indebtedness to the published works of Johnston will be 

 evident to the reader throughout this paper. I have received 

 still greater assistance from many extended conferences with 

 Professor Johnston, in which he has freely shared with me his 

 unpublished observations and stimulatng suggestions. The full 

 extent of this obligation it is not necessary, nor indeed possible, 

 for me to indicate here. It should, moreover, be added that, 

 while many parts of this discussion have been greatly influenced 

 and I trust improved by these conferences, the responsibility 

 for the morphological views here expressed is wholly my own. 



AMPHIBIA 



I have studied an extensive series of sections of larval and adult 

 Amblystoma, Necturus and various species of frogs, prepared 

 by different methods, including the silver methods of Golgi and 

 Ramon y Cajal, the method of Weigert, a toluidin blue modifica- 

 tion of Nissl's method and various general embryological methods. 

 Most of this material, except the larval Necturus which I studied 

 through the courtesy of Professor Minot in the Harvard Embry- 

 ological Collection, was prepared by Mr. P. S. McKibben of the 

 Department of Anatomy, University of Chicago, to whose kind- 

 ness and skill I am greatly indebted. I have also examined a se- 

 ries of cross sections through the head of Petromyzon (Ichthy- 

 omyzon concolor) prepared and kindly loaned to me by Dr. 

 Charles Brookover. 



In the Amphibia the wall of the cerebral hemisphere is naturally 

 divided into five parts. Not to prejudice the morphological sig- 

 nificance of these parts at the start, I shall call them simply 

 olfactory bulb, ventro-medial, ventro-lateral, dorso-lateral and 

 dorso-medial parts. They are especially distinct in the adult 

 frog and are termed by Gaupp respectively lobus olfactorius, 



