2 54 The Ohio Naturalist [Vol. VIII, No. 4, 



As to whether the placodal portions of the communis gangHa 

 give rise to special visceral fibres only, or to both special and 

 general visceral fibres there is less certainty. The facts on which 

 we may hazard a conclusion are as follows: 



Every cranial nerve containing gustatory fibres comes from 

 a gangHon which can be traced wholi}^ or in part t') an evi 

 branchial placode. The VII, the cranial ganglion supplying by 

 far the largest number of gustatory fibres comes from the largest 

 epibranchial placode. 



The X, the cranial ganglion supplying the largest general 

 visceral component contains the largest neural crest element. 



The smallest general visceral component is apparently in the 

 VII nerve and there is possibly a small neural crest element in 

 the gerniculate ganglion. 



The IX nerve is most interesting in this connection. I am 

 unable to find any neural crest cells in the communis ganglion of 

 the IX nerve and Professor Herrick describes it as supph'ing 

 taste buds throughout its whole area of distribution and makes 

 no mention of its supplying general mucuos surfaces. 



If this is true we have a pure special visceral or gustatory 

 nerve coming from a pure placodal ganglion in the case of the IX, 

 and a very reasonable deduction from this is, that the placodes 

 give rise to that portion of the communis ganglion which supplies 

 special visceral or gustatory fibres, the portion supplying 

 general visceral fibres coming from the neural crest. 



The latter is homologous then in origin with the general 

 visceral ganglia of the cord, but differs from them in that it 

 dissociates itself from the general cutaneous cranial ganglia and 

 fuses with that derived from the placode. 



The general cutaneous ganglia of the cranial nerves are 

 quite distinct and there is even less excuse for confusing the 

 cutaneous and visceral ganglion in the embryo than there is in 

 the adult. 



If the epibranchial placodes give rise to the gustatory por- 

 tions of the communis ganglia, we must look on the gustatory 

 nerves as comprising a special visceral system because they end 

 in visceral centers in the brain, and not because of any similarity 

 in origin of the general and special visceral ganglia or because of 

 the method of distribution of the gustatory organs. 



The ganglia are in no immediate sense related to general 

 visceral ganglia in mode of origin, and the gustatory organs arc 

 highly speciali.:ed and may be mainly ectodermic in position so 

 that I think the term special communis ought to be applied with 

 central brain connections always in mind as the justification for 

 the term and this seems to be generally done. 



This generalization in regard to the origin of the gustatory 

 fibres is too far reaching to be rendered safe by a study of one 



