MIDBRAIN AND THALAMUS OF NECTURUS 219 



In the present contribution this analysis is continued into 

 the midbrain and its connections, using Necturus maculatus as 

 the type. Here is included, then, as complete an analysis as 

 the material at hand permits of the midbrain of Necturus. The 

 structure and connections of the diencephalon are included only 

 in so far (^^dth few exceptions) as these are necessary for an 

 understanding of the mesencephalic connections. A fuller 

 discussion of the amphibian diencephalon I hope to present in 

 a subsequent paper. 



The general structure of the brain of Necturus has been very 

 clearly described in the work of Kingsbury ('95), to which refer- 

 ence has already been made, and the chief fiber tracts are there 

 illustrated, so far as they can be shown by the Weigert method. 

 Osborn ('87 and '88) had previously described some features of 

 this brain with good figures, Miller in 1900 published two figures 

 of a wax model, Johnston in several works (e.g., '05, '06) has 

 made references to it, Warren in 1905 described the develop- 

 ment of the pineal region and gave a figure of the adult brain, 

 and von Kupffer ('06) described the brain of a 24 mm. embryo. 

 In 1911 McKibben published a drawing of the ventricular sur- 

 face after section in the sagittal plane and a series of sketches 

 of cross sections through the forebrain illustrating the general 

 relations, together with a detailed description of the nervus 

 terminalis. The same author in 1913 described the eye-muscle 

 nerves with accurate figures of dorsal and ventral views of the 

 brain after fixation in situ in the cranium. Norris and Buckley 

 ('11) briefly described the cranial nerves of Necturus and men- 

 tioned the pre\4ous literature on the subject, and in another 

 short paper Norris ('11) discussed the phylogenetic rank of 

 Necturus. Rothig in 1911 published a brief account of the 

 myelinated fiber tracts of the cerebral hemispheres with an 

 excellent series of figures of cross sections, which add some de- 

 tails to the earlier account of Kingsbury, and in 1912 he con- 

 tributed some further information on the internal structure of 

 this brain and of that of other urodeles. 



In this descriptive paper we shall not undertake a summary 

 of the contents of the papers just cited or of the literature on the 



