132 IOWA ACADEMY OF SCIENCE 



In fact, the resemblances to the condition in the latter form are very 

 close and suggestive. 



Kingsbury (1895) describes the olfactory nerve of the adult Necturus 

 as arising "from the ventro-lateral angle of the olfactory lobes as a 

 single root." By the study of horizontal sections the writers have 

 found that the olfactory glomeruli show an evident arrangement in two 

 groups ; a posterior dorsal and an anterior ventral group. Correspond- 

 ing there are two groups of fibers or roots, which very soon combine 

 to form the long olfactory nerve. From the interweaving of the fibers 

 it is impossible to correlate the distribution of the divisions of the 

 olfactory nerve with their origin from the brain. In a larval Necturus 

 of 35 mm. length the olfactory capsule lies lateral and but little an- 

 terior to the olfactory lobe, and in consequence the olfactory nerve is 

 short. It passes through the cranial wall by three apertures, one dor- 

 sal and posterior and the other two more ventral and anterior. The 

 fibers that pass through the posterior opening supply chiefly the pos- 

 terior dorsal and lateral olfactory epithelium, some' branches also pass- 

 ing along the median nasal wall well toward the anterior portion. The 

 nerves passing through the anterior openings supply the anterior part 

 of the olfactory epithelium. The arrangement of the glomeruli into 

 anterior and posterior groups is not as evident as in the adult. The 

 arrangement of the glomeruli in the adult is strongly suggestive of the 

 condition described by Lee (1893) in Spelerpes fuscus and Salaman- 

 drina perspicillata. where he finds two distinct groups of glomeruli 

 with two olfactory roots. In Spelerpes bilineatus the writers have 

 found the two-fold grouping of the glomeruli even more evident than 

 in Necturus, and as in the latter more distinct in the adult than in the 

 larva. It is evident that the contention of Lee that this double nature 

 of the olfactory nerve in many, if not all. Amphibia has nothing to do 

 with the innervation of Jacobson's organ, is well founded for in Nec- 

 turus the latter organ is absent. 



No account is here given of the optic and the eye-muscle nerves in 

 Necturus. Their poorly developed condition has rendered the study 

 of the eye-muscle nerves difficult, and a report on them is deferred to a 

 later time. 



The trigeminal nerve has few characteristics worthy of especial men- 

 tion. Its general cutaneous elements are distributed to four nerves: 

 (1) the ramus mandibularis, (2) the ramus ophthalmicus profundus, 

 (3) the so-called ramvis maxillaris that joins the r. buccalis VII, (4) a 

 small component that passes into the r. ophthalmicus superficialis VII. 

 A small branch of the r. mandibularis enters a canal in the lower jaw 



