58 MR. T. H. HUXLEY ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA. 
Middendorf, in his elaborate Monograph upon Chiton (Malacozoologia Rossica), 
gives a very careful and detailed description of the buccal apparatus in that Mol- 
Insk, but equally fails in rendering its action clear. 
He gives the name of tongue exclusively to a ‘'bifid papillose organ, surrounded 
by circular folds, which consists mostly of vascular branches, between which masses 
of muscle are interwoven;” this is placed in the floor of the buccal cavity in fiont 
of, and below the buccal mass. 
To what is commonly known as the tongue, he gives the name of “ radula, leib- 
platte.” The dentigerous plate is the “lamina radulee,” its expanded portion the 
“orbis radulse.” What I have called the buccal cartilages are his “ folliculi 
motores.” 
It is difficult to come at any clear understanding of Middendorf’s views, but so 
far as I can comprehend them, he appears to consider that the “ lamina radulee acts 
as a sort of elastic file pushed from behind by a special muscle, the “ curvator 
radulse,” and supported and steadied by the “ folliculi motores.” 
Vox SiEBOLD says^, “this organ (the tongue), by its protrusion and retraction, is 
made use of by the Cephalophora as an ingestive apparatus.” He says nothing about 
the buccal cartilages or the minute structure of the organ. 
When I first examined this apparatus carefully six or seven years ago in Buccinum, 
I was convinced that Cuvier had mistaken its mode of operation, and further 
observation has only strengthened that conviction. 
I have already described the manner in which the apparatus may be seen working 
in FiroloUes and Atlanta, and I propose now to demonstrate that from the anatomical 
arrangements the “tongue” has the same chain saw-like mode of operation through- 
out the Cephalopoda and Gasteropoda. Perhaps Patella may be taken as the most 
convenient illustration, since the organ is here very large, and its parts are distinct 
and well-developed. 
In Patella (Plate V. figs, 12, 13) it is an oblong mass, reddish, except where the 
tongue-plate shines with a somewhat greenish hue. It is bifid posteriorly, and has a 
sulcus along two-thirds of its upper surface. In this the tongue lies before it enters 
the cavity of the mouth. The opening of the cesophagus corresponds with about the 
anterior fourth of the upper surface of the buccal mass. 
To the postero-lateral angles of the mass its extrinsic protractor muscles are attached, 
two on each side. They go to be inserted into the cephalic parietes, two in front of 
and above, and two behind the supraoesophageal ganglia. The lower ones are united 
so as to form a broad muscular plate. Two small muscular bands are also sent from 
the anterior angles of the buccal mass to the skin of the head. 
' When the muscular expansion formed by the lower protractors is removed, four or 
five muscular bands (fig. 12 fi) are perceived inserted by their posterior extremities into 
the posterior and lower part of the “buccal cartilages,” and converging anteriorly to 
be inserted into the lower edge of an “ elastic plate.” 
* Vergleichende Anatomie, p. 320. 
