Marsh. 217 



capable of separation ; but we can soon create a lively diver- 

 sion. In goes the point of a stick, and away the constituent 

 atoms of that heterogeneous mass scatter in all directions. 

 There is a thorough-going little tadpole with a large head 

 and tail, and two lateral gill-tufts by the side of its head, 

 through the thin membrane of which the blood passes whilst 

 being purified. Notice how it gulps the water into its 

 mouth, for this little fellow breathes like a fish at present, 

 and the water taken in at its mouth is forced into the gill- 

 chambers, where it passes over the layers' of thin membrane 

 forming the gills, and then out of the gill-covers at the back, 

 whilst the oxygen required by the tadpole is absorbed by 

 the blood from the water, as it passes over the gills. 



How does the blood get to the gills ? you ask. Well, all 

 the blood in the two chambers into which the heart of the 

 tadpole is divided is impure, and when the heart contracts, 

 the blood is driven direct to the gills for purification. Then 

 it is carried all over the body, where it becomes impure 

 again ; then it goes back to the heart, thence to the gills, 

 and once more over the body. Ah ! there is another tadpole, 

 rather larger than the last one, which has commenced to 

 grow its hind legs, whilst yonder is a fellow whose arms are 

 growing as well. Here is a remarkable fellow ! He is 

 quite like a toad, except that he has still his taddy's tail ; 

 but he will soon lose that now. 



You see, then, that the toad undergoes a great deal of 

 change when young. From an egg it becomes a tadpole, 

 then it grows a pair of hind limbs, and later, a pair of hands ; 

 after this it loses its gill- tufts, and finally its tail, and 

 becomes a little toad. But these outside changes are accom- 

 panied with equally important internal changes, for the 



