i6 



BIOLOGY AND HUMAN LIFE 



ment has on each side a small eardrum, or tympanum (see 

 Fig. 8). The hindmost segment bears special structures that 

 have to do with the throwing out of refuse {feces), and others 



connected with reproduction. In 

 the female these terminal parts to- 

 gether constitute the ovipositor, or 

 egg-laying organ. 



11. A representative mammal — 

 man {Homo sapiens). We are so 

 familiar with this species that we 

 need merely to recall the main fea- 

 tures of the outward form and struc- 

 ture. Like the insect, this mammal 

 has a main body, with a distinct 

 head at the anterior end and append- 

 ages (two pairs) attached to the 

 trunk— one pair at the anterior end 

 (the arms), the other pair at the 

 posterior end (the legs). We see, 

 further, that both animals have a definite bilateral (two-sided 

 symmetry, the right and left halves being almost identical in 

 form {although opposite in placing and facing). Certain kinds 



Fig. 7. Breathing tubes in 

 insects 



s, the spiracles in the side of the 



body, opening into the trachese t, 



which branch repeatedly and bring 



air to all the tissues 



Fig. 8. The main divisions of an insect's body 



In the grasshopper, as in other insects, the body is made up of a rather distinct head 

 at the front end; the main "trunk," or abdomen : and, between these, the thorax, 

 which bears both the legs and the wings. Near the front end of the abdomen the 



grasshopper has a rather large eardrum 



of parts are common to the two animals, although these cor- 

 responding parts (for example, mouth, ear, eye, leg) are very 

 different in structure; and there are other differences which 



