366 F. L. LANDACRE 



The introduction of the term ' branchial sense organ' by Fro- 

 riep and Beard seems unfortunate. Froriep ('85) applied it to 

 the epibranchial placodes of mammals, and Beard ('85-'86) to 

 both epibranchial and dorso-lateral placodes apparently, and the 

 term is used by Wilson ('91) in his paper on the sea bass. In all 

 cases the term seems an unfortunate one. The epibranchial 

 placodes of Ameiurus have no resemblance whatever to sense 

 organs, particularly to gustatory organs, and the dorso-lateral 

 placodes while resembling, in Ameiurus, lateral line organs do not 

 give rise to lateral line organs. This is true in Necturus, as shown 

 by Miss Piatt ('95). The branchial sense organs of Wilson are 

 apparently the dorso-lateral placodes. Whatever may have been 

 the phylogenetic history of these placodes, it is much better to 

 designate them in such a way as not to commit oneself to a theory 

 as to their phylogenetic origin until it can be shown what that 

 origin was. I have, therefore, followed von Kupffer ('94) and 

 have used the term 'placode' exclusively. The distinction brought 

 out (p. 56-57) in the discussion of the relation of the pre- and post- 

 auditory placodes to the specific lateral line organs finds a strik- 

 ing parallel in the relations of the epibranchial placodes to their 

 specific sense organs, the taste buds. 



The lateral line organs arise in Ameiurus as definitely localized 

 differentiations of the epidermis, and are not derived from the 

 dorso-lateral placodes (pre-andpostauditory placodes of Ameiurus) , 

 although they receive their innervation from ganglia derived from 

 these placodes in the case of the X, IX and the VIII nerves. 



The taste buds bear the same relation to the epibranchial 

 placodes, as shown by the writer (Landacre '07). The taste buds 

 appear simultaneously at the extreme anterior end of the oral 

 cavity (ectoderm) and on the endoderm of the first three gill 

 arches and spread posteriorally from the gills into the pharynx 

 and oesophagus and from the anterior end of the oral cavity back 

 into the mouth and externally over the lips, barbules and outer 

 surface of the head and finally over the whole body. 



The taste buds appear in well defined groups determined largely 

 by the distribution of the rami of the nerves carrying gustatory 

 fibres. These groups are isolated at first and later become con- 



