DEVELOPMENT OF THE COMMON FROG. 107 



Plate XIV. 



59. A drawing was made of the mouth of a tadpole. 

 The teeth on the lips were in the form of combs — that is, 

 in long rows set in narrow white bars which appeared to 

 consist of cartilage. In the upper lip were five sets, the first 

 or outermost of which was complete from side to side; the 

 second formed a pair not meeting in the middle; the third 

 consisted of a short length on each side, the fourth a longer 

 set on each side, and the fifth a very small comb on each 

 side with only three small teeth. The lower lip had four 

 sets, all of them divided at or near the middle. 



59 (2). A drawing was made of the outlet from the gill- 

 chambers, as seen from above. 



59 (3). On laying bare the right gill the toes of the 

 right fore limb were found pointing forwards ; the limb 

 was traced backwards, and a drawing made of as much of 

 it as could be exposed. Its development was about equal 

 to that of the hind limb of the same tadpole. 



60. The skin of the right side of a tadpole was cut away, 

 exposing the right gill with the right fore leg resting upon 

 it, the liver, and a loop of the intestine. An enlarged 

 drawing of the whole animal was made showing these 

 parts. 



60 (2). A drawing was made of the right fore leg under 

 the microscope with the two-inch object-glass. 



60 (3) . A corresponding drawing was made of the right 

 hind limb, showing the comparative size and the agreement 

 in development of the two. 



The food of the tadpoles has been exclusively vegetable ; 

 they are seen constantly grazing on the confervse round 

 the sides of the pond. 



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