484. Development of Mouth and Gills in Bdellostoma 
idea originating with Ayers and Jackson as one might conclude from 
reading their papers of 1900. Those authors, it appears, could not have 
considered these early views in spite of the fact that they are either men- 
tioned or discussed in the papers of J. Miiller and P. Fiirbringer 
which Ayers and Jackson have placed in the literature list of their 
paper. 
As Ayers and Jackson state, morphologists followed for a long time 
Miiller in accepting, not his own or original view, but Home’s idea 
that the dental-plate was a tongue. And even Huxley, in attempt- 
ing to locate the jaw cartilages of Petromyzon failed to deter- 
mine that the tongue was really a part of the jaw structures. Ayers 
and Jackson in their work on the skeleton of Bdellostoma interpreted the 
cartilages of the tooth plate to be in reality lower jaw cartilages, but 
this so far as I am able to gather from their paper is all they contribute 
towards proving the matter. As far as the musculature is concerned 
they merely note, “‘ The huge club-shaped ‘ tongue’ muscle is made up of 
the muscles belonging to this arch (meaning the mandibular). These 
muscles have been in Bdellostoma entirely separated from their attach- 
ment to the palato-quadrate, and have been translated to their present 
position in a manner which will be made clear in a subsequent paper,” 
but no description of this process has since appeared. 
It had, however, already been shown by Miiller and Firbringer that 
the muscles manipulating the tongue are innervated by the ramus mandi- 
bularis of the trigeminus nerve, 1. ¢., the true lower jaw nerve. Subse- 
quently Allis, 03, in studies on the adult, and Kupffer, 00, (in his 
figures) on the embryo, have also shown that the dental plate and its 
muscles are innervated by the true lower jaw nerve. And during the 
past year Miss Worthington, working under the direction of Dr. Ayers, 
has traced the cranial nerves and practically repeated Allis’ work. She 
does not, however, refer to this paper and was evidently unaware that her 
results had been anticipated in spite of the fact that the admirable paper 
of Allis’ had appeared two years earlier. 
I do not wish to appear unsympathetic to the work of Ayers and 
Jackson: indeed, in the following pages I shall join with them in 
defending the thesis that the so-called “tongue” or dental-plate in 
myxinoids is really homologous with the vertebrate lower jaw. I must, 
however, call attention to some of their errors (which I think have in part 
resulted from their inadequate knowledge of theliterature) in my endeavor 
to place the results of the present paper in a clearer light. Thus they 
state, for example, that all anatomists “ have apparently overlooked the 
