40 Dr. Waller on the Development of the 



the month. By the time the fore-limbs make their way through 

 the integument's, all the teeth at the jaws have been east off, the 

 folds of the lips and their papillre are entirely lost, and the skin 

 is tightly bound around the mouth, which has now assumed its 

 definite shape, except that its opening is narrowed by a fold of 

 skin at the angles. Gradually these folds decrease, until the 

 angles of the mouth recede back to the articulation of the ja.ws. 

 This change is accomplished by the time the tail is atrophied, 

 and the animal has assumed its terrestrial habits. 



The metamorphosis in the animal's habits is not less marked. 

 It now seeks the land, and quickly dies if kept in the water. 

 The indiscriminate voracity of the tadpole no longer exists ; it 

 rejects all dead food, and subsists exclusively on live insects. 

 The situation of the labial papillae in the tadpole is well-adapted 

 for the senses of touch and of taste. Those exterior to the lips 

 are mostly adapted for tactile purposes. The activity of this 

 sense is e\ ident when the animal is obsei-ved hovering aroimd 

 some floating object, of which it evidently takes cognizance by 

 some tactile power located in this region. The papilla3 inside 

 the lips are more suitably disposed for receiving sapid impres- 

 sions, being in close proximity with the food after it has been 

 comminuted by the teeth. In Fishes, that class of animals to 

 which the tadpole presents the greatest analogies, we find grouped 

 around the mouth organs which appear strictly homologous to 

 those under examination. Such are the tentacles about the 

 mouth of the individuals composing the Cyjirinoid and Siluroid 

 families. The fleshy process at the symphysis of the Cod is 

 probably the same organ reduced to a rudimentary state. In 

 the Lancelot*, "the vertically -tissm-ed aperture of the mouth is 

 ,jpr'o\ ided oil each side with a scries of long, slender-jomted and 

 ciliated tentacula, which mainly, by the perpetual vortex they 

 cause in the sm-rounding water, brmg the animalcular nutriment 

 within the grasp of the pharynx." 



The conical processes of the tadpole probably possess a similar 

 power, only in much more limited degree, as they are abundantly 

 provided ■\\ith well-developed cilia of a very active character. 



The tongue of the tadpole makes its appearance at the time 

 that the mouth assumes its definite shape, which we have stated 

 occurs contemporaneously with the evolution of the fore-limbs. 

 At the earliest stage the tongue offers inequalities, where, after 

 congestion, are red jioints of engorged blood, the first appear- 

 ance of fungiform papUlte. In a fragment slightly compressed 

 between glass, these bodies are seen to project at the borders. 

 They ai'e nearly globular, and are seated immediately on the 

 membrane without any apparent stem, and are about yi^dth of 

 * Ohch, Comparative Anatomy, p. 22!). 



