The Story of Evolution 95 



after well-being throughout the history of animal life. In the 

 same way with mankind, migrations were prompted by the set- 

 ting in of prolonged drought, by over-population, and by the 

 spirit of adventure. (2) In Amphibians for the first time the 

 non-digitate paired fins of fishes were replaced by limbs with 

 fingers and toes. This implied an advantageous power of grasp- 

 ing, of holding firm, of putting food into the mouth, of feeling 

 things in three dimensions. (3) We cannot be positive in regard 

 to the soft parts of the ancient Amphibians known only as fossils, 

 but if they were in a general way like the frogs and toads, newts 

 and salamanders of the present day, we may say that they made 

 among other acquisitions the following: true ventral lungs, a 

 three-chambered heart, a movable tongue, a drum to the ear, and 

 lids to the eyes. It is very interesting to find that though the 

 tongue of the tadpole has some muscle-fibres in it, they are not 

 strong enough to effect movement, recalling the tongue of fishes, 

 which has not any muscles at all. Gradually, as the tadpole be- 

 comes a frog, the muscle-fibres grow in strength, and make it 

 possible for the full-grown creature to shoot out its tongue upon 

 insects. This is probably a recapitulation of what was accom- 

 plished in the course of millennia in the history of the Amphibian 

 race. (4) Another acquisition made by Amphibians was a voice, 

 due, as in ourselves, to the rapid passage of air over taut mem- 

 branes (vocal cords) stretched in the larynx. It is an interesting 

 fact that for millions of years there was upon the earth no sound 

 of life at all, only the noise of wind and wave, thunder and ava- 

 lanche. Apart from the instrumental music of some insects, per- 

 haps beginning in the Carboniferous, the first vital sounds were 

 due to Amphibians, and theirs certainly was the first voice 

 surely one of the great steps in organic evolution. 



Evolution of the Voice 



The first use of the voice was probably that indicated by 

 our frogs and toads it serves as a sex-call. That is the meaning 



