24 Journal of Comparative Neurology. 



the development of the oblongata of the human brain show a 

 similar submergence of the fasc. solitarius, at first a superficial 

 tract, by the ventral growth of dorsal regions (Rautenlippe)/ 

 and I have no doubt that when the development of the oblong- 

 ata in Teleosts is studied with this point in view, a similar 

 change will be found to take place here and at some stage the 

 spinal V tract to be superficial as in Urodeles and Ganoids. 



Among Teleosts there exist wonderful modifications in 

 the development of these systems. The simplest condition is 

 found in the two representatives of the order Haplomi which 

 were examined, Esox and Fundulus, where the regions have as 

 great a cephalo-caudal extension as in Ganoids and no fusions 

 occur. In the Acanthopteri there is a fusion of the tubercula 

 acustica across the meson, constant in the representatives of 

 the four of its families that were examined. In Clupea the 

 acusticums are fused and more concentrated, so that the appear- 

 ance is that of a lobe of the cerebellum. In the representatives 

 of the other two orders, there is a more or less marked develop- 

 ment of the communis system, especially of the preauditory por- 

 tion of it, together with a more or less evident concentration of 

 oblongatal structures (cephalization) which has not yet been 

 properly estimated. Amimiis is simplest, with no secondary fu- 

 sion of any portion of the oblongata, although the preauditory 

 portion of the fasciculus communis tract is greatly developed. 

 In the Eventognathi there exists an increasing complexity in the 

 structure of the fasciculus communis, and fusion of the cephalic 

 end (preauditory), of the two tracts as well as of the acusticums 

 occurs. In Notcmigonus the relation is simplest since here the 

 lobi vagi do not overlap the fused lobi trigemini as occurs in 

 other cyprinoids, notably Cyprimis. In the Catostomidae, the 

 development is more marked. Here (Catostomus) the enormous 

 lobi vagi extend cephalad over the lobi trigemini so as to near- 

 ly or quite conceal it and the fused acusticums, and there is a 



1 "Within a few days the Rautenlippe unites with the main fold of the zone 

 and continues to grow toward the median ventral line passing outside of the 

 tractus solitarius, which thus becomes buried, and, instead of lying super- 

 ficially, is thereafter deep below the outer surface." Minot, p. 666- 



