9 8 THE BOOK OF NATURE STUDY 



appearance of myriads of the little black creatures, still furnished 

 with stumps of tails. 



We may follow first in outline the course of the development 

 and then point out its special interest. After hatching, the tiny 

 tadpoles wriggle out of the mass of jelly, and swim to a piece 

 of waterweed to which they attach themselves in rows by a 

 sticky substance produced in the head region. At this stage 

 they remain more or less motionless, only swimming a short 

 distance from the weed if disturbed. After a few days, how- 

 ever, external gills develop, and as the internal store of food on 

 which the little creature has been living is exhausted, it becomes 

 more active, swimming about in search of food, which consists 

 at this stage of waterweed. Growth is rapid ; the little tadpole 

 acquires a better developed tail, and the external gills disappear, 

 being replaced by more efficient internal gills, like those of a 

 fish. Though theoretically vegetarian, in captivity at least, 

 the tadpoles will begin at an early stage to take animal food 

 also they will devour their dead brethren, and nibble clean 

 the skeleton of a small animal put into the water. They often 

 occur in ponds in enormous numbers, and their graceful evolutions 

 in the water are well worth watching. 



After about two months of larval life, the hind limbs begin 

 to appear as buds. They increase in length, but for long are 

 useless and helpless, trailing behind the tadpole as it swims, and 

 being apparently incapable of being bent. At this stage the 

 tadpole begins to come to the surface to gulp in a bubble of air, 

 a fact which shows that the lungs are developing, and that the 

 animal is ceasing to depend solely upon its gills. In captivity, 

 especially if the water is allowed to get foul, the lungs seem to 

 develop rapidly, and the animal depends upon them largely. On 

 the other hand, if excessive care be taken to keep the water pure 

 the lungs will develop slowly, and it is even possible to delay 

 their appearance for months by stretching a fine net immediately 

 below the surface of the water, and thus preventing the tadpoles 

 from coming to the surface to breathe. 



After the hind limbs have reached their full size, the fore 

 limbs appear suddenly, usually in the course of a single night. 

 Growth at such a rapid rate is of course impossible, and it will be 



