A FEW FACTS ABOUT ZOOLOGY. 



that the jointed plan controls the organization of both. The 

 body of the lobster is divided into a succession of joints or 

 rings like the worm; the fact that the front limbs of the 

 lobster are soldered together, so as to make stiff the front 

 region of the body, inclosing the head and chest, while only 

 the hind rings remain movable, thus forming a flexible tail, 

 does not alter the general structure, which consists, in both 

 worm and lobster, of a body built of articulations or joints. 

 Highest in this type are the insects; among these are in- 

 cluded spiders, centipedes, and winged insects. In all these 

 we find a breathing apparatus far superior to the respiratory 

 organs of the worms, or the more highly organized gills of 

 the lobster. 



This apparatus con- 

 sists of air-holes on 

 the side of the body, 

 connected with a sys- 

 tem of tubes extend- 

 ing into the body, 

 and admitting air to 

 all parts of it. In the 

 winged insects this 

 system is very elab- 

 orate, filling the body 

 with air to such a de- 



gree as to render it 

 exceedingly light, 

 and adapted to easy 

 and rapid flight. A 

 careful examination 

 will not fail to show 

 the jointed character FlG 5 



of the insect. This 



may be readily seen by studying the diagram shown in Fig. & 

 The changes which an insect undergoes are well known. Yor< 



