120 DR. THOMAS ALCOCK ON THE 



The mouth consists of a pair of strong brown horny 

 beaks with serrated edges, and is surrounded by a broad 

 expanded sheet of white fleshy membrane, quite distinct 

 in character from the skin of the body ; it is irregularly 

 frilled and scolloped at the edges, and, being continuous 

 at the sides, forms, when spread out, an irregular circular 

 figure, in which the distinction of upper and lower lip is 

 marked only by position. The inner or front surface is 

 furnished with long ranges of small brown teeth set upon 

 white frames or backs, so that they resemble combs. 

 There is some irregularity in their number and arrange- 

 ment in different specimens ; but usually there are three 

 sets in the upper and four in the lower lip. The two inner 

 sets in the upper lip are interrupted in the middle by the 

 arched form of the upper beak ; and there are also often 

 one or two pairs of very small combs, each with only three 

 or four teeth, placed between the longer sets. The food 

 of tadpoles is indifferently vegetable or animal, but more 

 commonly vegetable ; when animal it consists of the flesh 

 of any dead creature that may chance to be in the water. 

 The lips are applied in the manner of a sucker, and give a 

 firm hold for the action of the beaks. 



The alimentary canal consists of a long simple tube of 

 equal diameter throughout ; and from the point where it 

 leaves the liver to its termination it is laid together double, 

 and is coiled round and round, filling the left half of the 

 abdominal cavity, and forming in its final coils the regular 

 flat spiral, with the loop of the doubled intestine in the 

 centre, which is seen on removing the skin of the ventral 

 surface of the abdomen. This period occupies twenty 

 days. 



Fourth Period. — In this period, extending from the fif- 

 tieth to the seventy-fourth day, eager feeding and rapid 

 growth continue. The developments which take place in 



