CRANIAL GANGLIA OF AMBLYSTOMA 423 



the epibranchial placode of the first true gill. Since Herrick 

 ('07)2 ]^ad found only gustatory fibers arising from the visceral 

 ganglion of IX, Landacre naturally concludes that the epibran- 

 chial placode of IX gives rise to the gangUonic cells from which 

 the gustatory fibers arise. He further expresses the opinion that 

 this is the function of the epibranchial placodes in all types of 

 vertebrates (Landacre, '12), since these placodes occur only on 

 those nerves of VII, IX, and X which contain special visceral 

 fibers, and since the relative size and growth of the epibranchial 

 placodes in Lepidosteus and Ameiurus seem to be in relation to 

 the area and time of appearance of taste buds supplied by fibers 

 from special visceral ganglia. Coghill ('16) finds conditions in 

 Amblystoma which seem to indicate that the visceral gangha of 

 VII, IX, and X all receive masses of cells from the epibranchial 

 placodes. 



There is also evidence that there are other placodes besides 

 those concerned in the formation of lateral-line gangUa, i.e., 

 general cutaneous placodes. Piatt ('96) notes in Necturus that 

 an ectodermal thickening above the eye appears to be concerned 

 in some manner with the formation of the ophthalmicus pro- 

 fundus V nerve. A similar fact has been recorded by Coghill ('16) 

 in Amblystoma and by Landacre ('12) in Lepidosteus, where in 

 early stages of the formation of the ganglion of the ophthalmicus 

 profundus V there is a distinct anchorage to the ectoderm over 

 the eye. The former made the interesting observation that it 

 was during this period, in which the anchorage is intact, that root 

 fibers make their connection with the brain. However, neither of 

 the latter investigators satisfied himself as to the significance of 

 this early contact. Coghill ('16) also found in the earliest of 

 his stages described, the 'non-motile,' an area of adhesion between 

 the distal end of the gasserian ganglion and the skin. It is ven- 

 tral to the primordium of the preauditory lateral-line organs and 

 is not so extensive nor so intimate as the adhesion of the oph- 

 thalmic ganglion and skin. 



2 A note included in Landacre's paper ('07) by C. J. Herrick on the distribution 

 of the IX nerve of Ameiurus melas. The conclusions from this reference are found 

 in Landacre's paper ('12), page 3. 



