98 



ANIMALS OF LAND AND SEA 



Land planarians are abundant in the ground and in pro- 

 tected situations in damp forests in the tropics, whence they 

 are frequently brought into our green-houses. They feed upon 



earth-worms. A 

 166 f O-^ /T^P??^ very few sorts of 



nemerteans Hve on 

 land; they are all 

 carnivorous. 



Abundant every- 

 where in all situa- 

 tions, free-living or 

 as parasites, are 

 multitudes of nema- 

 todes or thread- 

 worms and of proto- 

 zoans. For the most 

 part these are small 

 and hence not often 

 noticed; but they 

 must not be forgot- 

 ten. 



How can the con- 

 ditions of animal life 

 on land briefly be 

 described? 



Active animal life 

 exists at all temper- 

 atures from the 

 melting point of ice, 

 32°, to about 40° 

 below the boiling 

 point of water, and 

 from an air pressure of one atmosphere to a pressure of about 

 one third of that amount. Below the freezing point only those 

 animals remain active and feed which, like the birds and mam- 

 mals, create a special temperature in which they live insulated 

 from and independent of that of the air. 



Figs. 159-170. Beetles commonly found in houses. 

 For explanations of the figures see p. xvi. 



