528 



MR. D. W. DEVANESEN ON THE 



2. The Viscera. 



The second dermal ridge on the palate of this toad is a con- 

 spicuous structure stretching across from one eustachian opening 

 to the other, its edge being thrown into well-marked denticula- 

 tions. On laying open the pha,rynx*", one finds immediately 

 behind this ridge and in close contact with it and occupying 

 more or less the same level, a differentiated area of about 

 80 sq. mm. (text- fig. 1). Transverse sections through the same 

 revealed the fact that it consisted of closely-set, parallel, and 

 longitudinal reduplications of the mucous membrane of the 

 pharynx, each fold containing an extension of the basement mem- 

 brane (text-fig. 2). A fold is on an average 1 mm. in height ; 

 the highest folds are found in the middle, and from this place 

 the height of the folds on the sides gradually decreases. These 



Text-figure 1. 



" The Pharyngeal Organ of Cacopus sysfoma " exposed ; the lower jaw and the 

 floor of the mouth Ihave been cut awaj'. L., lamellae arranged lengthwise ; 

 R., the first, short, R.', the second, long, denticulated ridge ; E., eustachian 

 opening ; V., vomer ; I. P., inner dark papilla on the toothless hind end of a 

 vomer (V.) ; O.P., an outer one on the vestigial palatine (P.) ; P.H., pharynx 

 cut open and deflected. 



folds show a faint tendency to anastomose, and their free edges 

 hanging down into the cavity of the pharynx, in the fresh 

 condition, appear swollen. This specialised area of the pharynx 

 may, in my opinion, be given the status of an organ for two 

 reasons : first, it is compact, having a certain definite outline, 

 a,nd it is restricted to a definite place, namely immediately 

 behind the second dermal ridge ; secondly, as the free end of the 

 tongue lies, when in a state of rest, underneath this area, and 

 since the presence of the intermaxillary glands is doubtful in 

 this toad, the structure in question is probably a substitute for 

 these glands, possessing a similar function ; the cells of the mucous 

 membrane in these folds are comparatively large and sacciform, 

 which facts are perhaps suggestive of their glandular nature. 



* That part of the alimentary canal between the second dermal ridge and the 

 stomach, I propose to call " the pharjaix," as it is much wider than it should be for an 

 CBSophagus which is probably unrejjresented in this toad. Tlie cavity enclosed 

 between this ridge and the jaws may be termed "the oral cavity." 



