FROGS 89 



mouth opens, and the little creature now feeds on water- 

 plants. The external gills become less evident, and even- 

 tually vanish. In the meanwhile internal gills have been 

 formed, and these gill slits are covered by a thin skin. 



In appearance the creature has made great changes. The 

 tail is now " a thing to be proud of," very different to that of 

 the young tadpole, and during this period, which is roughly 

 six weeks, the internal arrangements are very similar to those 

 of a fish. 



Up to this time the tadpoles seldom trouble to come to the 

 surface; the blood in the gills and the water containing air 

 meet, except for fine membranes, and thus an interchange of 

 gases takes place. But now the tadpole's habits alter ; it will 

 be seen to frequently swim to the surface in order to breathe, 

 for the lungs are being formed, and although the gills still 

 remain yet they no longer function as previously. Gradually 

 the gills atrophy, the eyes become larger, the lungs more 

 powerful, the digestive organs completely changed, the tail 

 becomes shorter and shorter, the feet webbed, and the little 

 creature with a stump of a tail evinces great eagerness to 

 escape out of the water. 



Occasionally tadpoles grow very large before forming their 

 limbs, or it may happen that the creature remains small 

 although maturing. 



Tadpoles are queer little creatures. They are very gre- 

 garious, loving to crowd together for no obvious reason. 

 Sometimes they are only too pleased to swim singly, but 

 occasionally nothing can be too crowded. Then they behave 

 in a similar manner to a crowd attempting to board a tramcar, 

 on the way to a football match. In fact, they rush and push 

 until one wonders that they do not injure themselves in their 

 violent struggles. Tadpoles evince some intelligence, and are 

 most expert dodgers when occasion needs. The poor little 

 creatures are always in trouble. Firstly, the enormous num- 

 bers means a possible shortage of food, and, in addition, they 

 have many enemies ; water-beetles, even the smallest, destroy 

 large numbers, the larva of Dytiscus will kill a score or more a 

 day. Even leeches will seize them, and more than one Nema- 

 tode worm passes part of its life history within the body of the 

 tadpole. 



The adult Rana becomes active early in the morning and 

 towards evening. During the day it hides away either in the 

 water, beneath stones, or under banks. Its food consists of 

 insects, which it captures by means of its tongue, used with 

 great rapidity. The body is enclothed in a loose skin, which 



