THE CRANIAL GANGLIA IX AMEITJR1 - 379 



fig. 73 which, however, is not taken through the largest portion of 

 the ganglion. Herrick ('01) does not give a description of the com- 

 munis ganglion of the Xth nerve in Ameiurus further than to call 

 attention to the fact that it is typical, and in describing Gadus 

 ('00) calls attention to the fact that it is similar to Menidia. In 

 Menidia (Herrick, '99; the fifth branchial nerve is larger than the 

 other four and gives rise not only to the fibres for the fifth gill 

 arch but also to the fibres for the great visceral and oesophageal 

 rami of the vagus. He also calls attention to the fact that in 

 Alenidia the ganglia of the glossopharyngeus and first branchial 

 ganglia of the vagus are composed of very large cells with medium 

 and small cells intermingled among them, and that as we go toward 

 the caudal end of the ganglionic complex, while there are still 

 found cells of various sizes, the smaller ones become increasingly 

 numerous, and suggests the hypothesis that the larger cells are 

 related to taste buds and the smaller ones to visceral fibres. 



The division of the extra-cranial Xth ganglion into four parts 

 can hardly be so distinct in Ameiurus as Herrick describes it in 

 Menidia, since in my oldest series the last two divisions are not 

 easy to distinguish and the fusion is probably much more marked 

 in the adult. At the time the fifth and sixth placodes of the Xth 

 nerve are present the lateral mass ganglion appears as a dense 

 mass of cells lying over the fourth and fifth gill slits. The first 

 two divisions of the Xth which are placodal in origin can be dis- 

 tinguished easily, and the first of these in any series is distinct 

 up to a late stage. 



We have here in the Xth nerve, then, a general cutaneous or 

 jugular ganglion derived from the lateral mass and lying intracran- 

 ially, and an extra-cranial visceral ganglion in which it is not pos- 

 sible to separate the placodal cells from the lateral mass cells which 

 greatly predominate over the cells derived from the fifth and sixth 

 epibranchial placodes. This whole ganglionic mass is described 

 by Herrick as a communis ganglion. We must add to this large 

 extra-cranial mass the two anterior placodal ganglia which however 

 can be distinguished easily from the combined lateral mass and 

 placodal portion. These relations are rendered clear by figs. 79. 

 80, 81, and 82. 



