FROM THALES TO LAMARCK 



25 



most remarkable elongation of the finger-joint, which is so con- 

 siderable that three of the inner fingers reach a length equal 

 to the joint length of the upper and fore arm. As the thumb has 

 no function to fulfil in flying it remains short but develops a 

 strong claw, by means of which the animals can climb or suspend 

 themselves. Between the fingers of this giant hand on one side 



FIG. 6. FLYING-FOXES (PteTOpUS 



and the hind extremities and the body on the other the thin skin 

 is expanded like a parachute. 



Some years ago geologists found in the upper strata of the 

 so-called lithographic slate of Bavaria (belonging to the Jurassic 

 Period) the fossil remains of a strange animal which was called 

 a Pterodactylus. A layman would at the first glance have 

 unhesitatingly declared it to be a bat, because of the enormous 



