458 EDWARD B. POULTON. 



or four, and penetrate the epithelium close together. The 

 ducts open freely on the lower surface of the tip over the 5 mm., 

 Avhere the gland-tubes occur; while above they open compara- 

 tively rarely between, but very abundantly on the papillae, and 

 especially towards the lower part of the anterior slope (fig. 4). 

 At this point the great majority of openings are found. Pos- 

 teriorly in this subregion, and in the posterior subregion itself, 

 the gland-ducts only open between the papillse. It seems very 

 likely that the papillae are rendered sticky by the glandular 

 secretion, and that the aquatic larvae, &c., which form this 

 animaFs food, are thus caused to adhere to them. It is not 

 likely, however, that the larvae are thus captured. A sticky 

 secretion would be of little use in the mud at the bottom of 

 ponds, and the tongue has such limited powers of movement, 

 and is set so far back (the tip is 13 mm. from the anterior 

 margin of the lower bill), that it is not probable that it can 

 even be protruded. The prey is caught by the bill, and the 

 animal is known to rapidly vibrate the lower bill in the water 

 like a duck, by which means the mud would be washed 

 away through its lateral grooves. The prey is thus held by 

 the ridges between the grooves and the flat surface of the 

 upper bill, and probably crushed to some extent by the pe- 

 culiar (and, I believe, undescribed) smooth, ridge-like horny 

 teeth, which are situated at the inner ends of the grooves (two 

 in each jaw). During all these processes the food is far from 

 reaching the posterior part of the singularly inflexible mouth. 

 Hence the importance of these large, adhesive, and (as will be 

 shown) highly tactile papillae on the anterior part of the 

 tongue. By their means the food can be drawn backwards to 

 the more efl^ective and corrugated teeth, to be thoroughly 

 crushed. Hence the importance of this excessive development 

 of glandular tissue at this particular part of the tongue. 



The imbricated arrangement, and sharp points and ridges of 

 the papillae, would also be of great importance in retaining 

 small insects, &c., which were caught by tlie adhesive anterior 

 papillary slopes. Thus an insect attempting to escape would 

 be met by the hard corneous posterior surfaces of the papillae 



