Herrick, Commissura Infma. 411 



median and lateral funicular nuclei and delicately medullated 

 fibers connecting the two median funicular nuclei. Farther ven- 

 trally arid extending nearly down to the canalis centralis are fine 

 fibers, chiefly unmedullated, passing between the formatio reticu- 

 laris of the two sides (fig. 2). Among the latter fibers are nu- 

 merous cells, some very small and some large (fig. 3; cf. fig. 5 of 

 Catostomus). These cells of the somatic commissural nucleus 

 constitute an extension of the adjacent formatio reticularis grisea 

 which, accordingly, is broadly continuous across the median line 

 above the canalis centralis. The large cells of this nucleus send 

 their neurites ventrally into the ventral cornu and perhaps the 

 ventral funiculi. The smaller cells seem to connect with the adja- 

 cent formatio reticularis. 



The splanchnic and somatic divisions of the commissura infima 

 are thus seen to be very similar, save in the fact that the somatic 

 division is not known to contain root fibers. Each contains com- 

 missural fibers from adjacejit primary centers and a median 

 nucleus whose efferent tracts reach the adjacent formatio reticu- 

 laris. These nuclei seem to have been differentiated from the 

 formatio reticularis grisea, the splanchnic nucleus being the more 

 highly specialized. 



I have elsewhere described these commissures in Gadus (1907, 

 p. 75-78) and found the typical relations with neither the somatic 

 nor the visceral elements especially differentiated, the somatic com- 

 ponent being considerably larger than the visceral (see figs. 3, 5, 

 6 and 7 of the paper cited). 



In Haploidonotus grunniens I find the same conditions as in 

 Gadus save that the visceral component is considerably larger. 



The commissura infima of cyprinoids. — ^In these fishes the 

 visceral element of this complex is greatly enlarged, without a 

 correspondmg modification of the somatic element. 



In the carp, Cyprinus, the morphologic relations are the same 

 as in Ameiurus with such modifications only as are caused by the 

 larger vagal lobes. The nucleus intermedius vagi seems to be 

 included in the motor layer of the vagal lobes (Herrick 1905, 

 p. 433). The visceral commissural nucleus is both larger and more 

 distinct than in Ameiurus. It is continuous headward with the 

 motor layer of the vagal lobes and under the caudal border of the 

 vagal lobes appears as a pair of pyriform swellings whose larger 

 ends are fused over the ventricle (fig. 4). The area of fusion con- 



