Kingsbury, Oblongata in Fishes. 21 



as Mayser shows, may be easily seen upon the ectal surface 

 until the acusticum covers it up. A drawing of the dorsal 

 aspect of the carp oblongata is shown in Fig. 2. (Comp. Fig. 

 4, of Perca.) 



In Catostomus (Figs. 21, 22, 25) the development of the 

 vagal lobes and tuberculum impar (fasciculus communis sys- 

 tem) is carried a step farther. The vagal lobes are enormous 

 and together with the cerebellum quite conceal the tuberculum 

 impar and acusticums. The very large sensory portion of the 

 Xth arises in two divisions and the motor farther ventrally 

 but dorsad of, or breaking through the spinal Vth tract (Fig. 

 21). Farther cephalad another quite large root enters the' 

 lobus vagi after the acusticum has already appeared in tran- 

 section (IX?). Figure 22 shows the overlapping of regions and 

 •Figure 25 may be compared with the similar section of Perca 

 Fig. 19. 



In none of the Eventognathi has a component of vagal fi- 

 bers from the spinal Vth tract been certainly detected. 



In General. The acusticum system in all these teleosts is 

 not only dorsal but extends laterad over the side of the ob- 

 longata covering and submerging the spinal Vth tract which un- 

 til its appearance is superficial. The general description of the 

 structural appearance of the fasciculus communis in Amia ap- 

 plies also to teleosts. 



In some forms the zone of small cells next the endyma is 

 quite thick, six or seven cells deep. In Amiurus this zone is 

 wanting and the cells are quite evenly dispersed through the re- 

 gion. When the system becomes greatly developed the dorsal 

 and lateral growth involves structures covered primarily (typi- 

 cally) by endyma until they become ectal and pial. Closely 

 associated with the communis system is the vagal motor nidus. 

 In Amia (Fig. 16) and the simple teleosts (Figs. 10, 12, 13, 23, 

 24) this lies ventrad of the fasciculus communis and is easily 

 recognized as forming no part with it, but in the cyprinoids 

 (and suckers) the eversion of the fasciculus communis involves 

 this region as well (Fig. 21.). Thus Mayser recognized in the 

 lobus vagi of the carp 5 zones or layers, — (i) fibers of the va- 



