220 C. JUDSON HERKICK 



urodele brain in general, including among others the papers of 

 Burckhardt ('91) on Triton and Ichthyophis, Mrs. Gage ('93) 

 on Diemyctylus, Hirsch-Tabor ('08) on Proteus, and Bindewald 

 ('14) on Amblystoma. 



Material and vietliods 



This contribution is based upon the study of an extensive 

 series of brains of adult Necturus maculosus (Raf.) prepared 

 by various methods by Dr. Paul S. McKibben, to whom I am 

 greatly indebted for generously placing his entire collection at 

 my disposal. This collection includes, among others, the fol- 

 lowing series of histological preparations: 



3 series by Weigert's method (transverse, sagittal and horizontal). 



3 series by Mallory's method for connective tissue (one transverse and two 



horizontal). 

 2 series by Heidenhain's iron hematoxylin and orange G (horizontal). 

 1 series by Ehrlich's hematoxylin (horizontal). 

 1 series by toluidin blue (transverse). 

 1 series by carmine and Lyons blue (transverse). 



4 series by vom Rath's method (transverse, sagittal and horizontal). 



9 series by Ram6n y Cajal's method (transverse, sagittal and horizontal). 

 40 series by Golgi's method (transverse, sagittal and horizontal). 

 1 series by the Cox-Golgi sublimate method (horizontal). 



The Weigert material was first fixed in a formalin-bichromate 

 mixture, followed by Miiller's fluid for several days, then em- 

 bedded in paraffin and stained by the original Weigert procedure 

 with remordanting in section with copper acetate. The destain- 

 ing was carried to the point where the myelinated fibers are 

 clearly differentiated and yet sufficient color is left in the back- 

 ground to render many of the unmyelinated fiber tracts and 

 the cell nuclei clearly recognizable. 



II. GENERAL MORPHOLOGY 



The brain of Necturus is simple from both the morphological 

 and the histological standpoints; and, though in some respects 

 perhaps degenerate, the general type is clearly very primitive. 



The mesencephalon and diencephalon form a continuous tube 

 with rather thin walls and extensive ventricular cavities, open- 



