METAMORPHOSIS OF TADPOLES. 



FAMILY OF ANOURA. 



6 This family is composed of frogs, toads, and some other 

 reptiles having nearly the same form. In them the metamor- 

 phosis is more complete than in all other animals of this order. 

 When the young tadpole first leaves the egg, it resembles a 

 little fish, and can live only in water. Its head is very large, its 

 belly protuberant, and its body unprovided with extremities, is 

 terminated by a compressed tail, which afterwards becomes 

 elongated, and much raised : its mouth is still a small, scarcely 

 perceptible hole, and its branchiae consist only of a tubercle 

 placed on each side of the posterior part of the head. p. on 

 These appendages very soon become lengthened, and l ^' *" 

 are divided into shreds, ( Fig. 30.) ; the eyes are percepti- 

 ble through the skin, and a transverse slit appears under 

 the neck, so as to form a sort of membranous operculum. 

 A little later, (Fig. 23, Page. 67.) the branchiae become 

 ramified, and the lips are covered by a sort of horny 

 beak, by the aid of which the animal fixes itself to vege- 

 tables, that form its chief food ; but this state does not T 

 last long. At the end of a few days the branchial fringes, which 

 float on each side of the neck, disappear, (Fig. 31.) and respira- 

 Fig. 31. tionis carried on by the assistance of small 



vascular tufts, placed along four cartilaginous 

 arches, situate under the throat, and pertain- 

 TADPOLE. ing to the hyoid bone. A membranous tuu.c, 



covered by the skin, envelopes these internal branchiae, to which 

 the water arrives by the mouth, passing through the intervals of 

 the arches of the hyoid bone ; finally, after having laved these 

 organs, this liquid escapes by one or two external slits, the situation 

 of which varies a little according to the species. The respiratory 

 apparatus, then, as we have said above, exactly resembles that 

 of fishes. Sometime after- 



wards, the posterior extremi- 

 ties of the Tadpole show 

 themselves, and are developed 

 little by little, (Fig. 32.) ; they 

 attain considerable length be- 

 fore the anterior extremities 

 are perceived. The latter are 

 developed beneath the skin, 

 which they penetrate at a later 

 period, (Fig. 33.) About the 



Fig. 32. 



6. What reptiles compose the family of Anoura ? What changes do the 

 animals of this family undergo in early life ? What is a Tadpole ? 



