THE TALE OF TADPOLES 35 



chambered heart, it probably re-enacts what took place 

 very long ago before the Coal-Measures were laid down 

 in Britain when Amphibians evolved from a Piscine stock. 

 But what took the race long ages to accomplish is achieved 

 by the individual in a few days, a fact so familiar that 

 we are apt to forget its marvellousness the mystery of 

 cumulative and condensed inheritance. 



With the acquisition of a mouth the larva begins to feed 

 eagerly, nibbling at plants in the water, and also eating 

 animal food. As a consequence it grows, and the food-canal, 

 in particular, becomes very long and coiled like a watch- 

 spring. It is interesting to notice the relatively great length 

 of the intestine during the predominantly vegetarian period, 

 for it is usual in the animal kingdom to find a diet of 

 vegetable food which is somewhat slowly digested 

 associated with length of food-canal or with some equiva- 

 lent of length. As the tail becomes stronger and the power 

 of locomotion increases, the horse-shoe shaped adhesive 

 organ is converted into two small discs which gradually 

 disappear. 



A new stage is marked by the appearance of the hind- 

 limbs as minute projecting buds at the boundary between 

 trunk and tail. Why should hind-limbs appear earlier 

 than the fore-limbs, which are, moreover, much shorter ? 

 Investigation shows that they begin to develop at the 

 same time a fact which gives additional point to the 

 question. The fore-limbs are delayed by the gill-cover, 

 which does not impede the hind-limbs, and they eventually 

 emerge, the left one through the " spiracle," the right one 

 by a rupture. Perhaps we get some insight into the 

 orderliness of developmental processes when we notice 

 that the microscopic lashes or cilia which have hitherto 

 covered the skin of the larva now disappear. In most 

 cases, except as regards reproduction, what we may call 



