43(> ANATOMY OF VERTEBRATES. 



Oxyglossus it is rounded, as in Toads and some Hylida>, e. g. 

 JElosia ; but here the whole margin adheres : the rarest form, in 

 anourous Batrachians, is that of Rhinoplirynus, in which the fore 

 part of the tongue is free. 1 In Serpents the tongue takes no other 

 share in the prehension of food than by the degree in which it may 

 assist in the act of drinking ; it is very long, slender, cylindrical, 

 protractile, consisting of a pair of muscular cylinders, in close 

 connection along the basal two thirds, but liberated from each 

 other, and tapering each to a point at the anterior third : these 

 are in constant vibration when the tongue is protruded, and are in 

 great part withdrawn, with the undivided body of the tongue, into 

 a sheath when the organ is retracted. This act is performed by 

 the ( glossohyoidei,' fig. 147, A ; protrusion is effected by the genio- 

 hyoidei, ib. z, z' . The orifice of the sheath is strengthened by a 

 pair of cartilaginous plates, on which other muscles act. 2 The 

 ununited symphysis of the mandible leaves a passage for the 

 tongue without the need of ( opening * the mouth : and the acts 

 of protrusion and retraction are usually seen to be frequently 

 repeated. The Amphisbcenid(B and Anguidce have short, thick, 

 hardly protractile, and sub-bifurcate tongues. 



The arboreal Chameleons, clinging on all fours to their tree 

 branch, depend wholly on their singularly extensile tongue for 

 the prehension of their volatile insect food. The movements of 

 this organ are as instantaneous as in the Toad and Frog, and 



296 



Tongue of the Chameleon partially extended. CCL. 



are due to combined muscular and elastic forces, acting within 

 the tongue and upon its supporting bones, with concomitant 

 modifications of the hyoid arch. The glosso-hyal is produced 

 into a long and cylindrical, fibro-cartilaginous style ; it penetrates 

 a fibrous sheath in the substance of the tongue, which, when 



1 It affords the character of Dr. Giinther's section Proteroglossa, CLXXV. 



2 CCXLI. p. 368, pi. 46, fig. 15. 



