THE FROG. 121 



Small arms or holders have been developed near the 

 mouth, or the part which is to form the mouth. At 

 first the mouth is small, and the nostrils and eyes are 

 not visible, but soon they begin to show themselves. 

 The bronchial tufts or gills grow, and are divided into 

 lobes, but the gelatinous envelope is not entirely got 

 rid of; this the young tadpole shortly disposes of by 

 its struggles, and the tadpole stage arrives at its maxi- 

 mum. The circulation of the blood in the gills or 

 branchiae can be well seen if the animal be placed 

 under a microscope. These parts are so transparent 

 that the globules of the blood, when highly magnified, 

 can be perceived. A change takes place in the 

 branchiae ; gradually they are transformed into more 

 perfect gills, four on each side, covered by a mem- 

 brane. The mouth and eyes increase in size, and the 

 filaments of the sides of the mouth disappear ; the 

 tail is now so expanded that the creature can swim 

 about in search of its food. 



But although we are describing a single tadpole, 

 yet there are many in the same stage which have 

 been produced from the numerous eggs or spawn, 

 and now form a shoal of greater or less extent, num- 

 bering perhaps hundreds. Further changes take 

 place, hind legs appear, at first under the skin near 

 the tail ; fore legs also. Simultaneously the gills 

 gradually disappear, for the lungs, which were in em- 

 bryo within the tadpole, expand, and it begins to 

 require atmospheric air ; as the animal becomes more 

 terrestrial and less of the nature of an aquatic creature, 

 the tail diminishes till it finally disappears, the legs 

 acquire their full proportions and strength, and it can 



