274 



HOW DO WE CLASSIFY ANIMALS? 



of had four toes on the fore and three toes on the hind feet. Thou- 

 sands of years later there existed a larger horse, the size of a sheep, 



with three toes on each foot. Through 

 a series of changes there was eventually 

 produced our present horse, an animal 

 with legs adapted for rapid locomotion, 

 with feet particularly fitted for life in 

 open fields, and with teeth which serve 

 well to seize and grind herbage. 



Practical Exercise 22. From outside sources 

 construct a diagram to show the different geologic 

 ages in this country. In what kind of rocks 

 would you look for fossils? Visit a museum 

 and describe some evidences of development seen 

 therein. What examples of change have you 

 seen in the world today ? List them. 



Self-Testing Exercise 



The (1) forms of (2) 



on the earth are believed to have been 

 very (3), while those that devel- 

 oped (4) are more (5). 



(6) or remains of animals and 



plants (7) in (8) tell us the 



story of (9) of life on the earth. 



Once, ages ago, there existed (10) 



horses having (11) toes on the fore 



feet. Later, as life on the earth changed, 

 there was a gradual development in these | 



(12) so that today we have horses 



with (13) toe, and longer legs fitted 



for more (14) locomotion. 



Tfesobippccs 



Cohippus Protorohxppus 



Redrawn from Photo ofAmer. 

 Mus. of Nat. Hist. 



In what ways has the horse 

 changed through the ages ? 



PROBLEM XI. WHAT IS MAN'S PLACE IN NATURE? 



There is no doubt that man is young compared to some animals, 

 but he is vastly older than was once believed. Very good evi- 

 dences in the form of skulls found in the caves of France and the 

 gravel pits of England show that man has lived on the earth tens of 



; 



