126 



MOVEMENT 



Most of the jointed animals, Arthropod a, run or crawl 

 about on their legs. Their legs move in a definite order. 

 Water-worms and leeches generally move by the undulations 

 of their bodies, swimming gracefully through the water. The 

 latter also loop like certain caterj^illars, Geometridae. 



Fig. 44. Underview of a Starfish, Echinaster sentus, with tube-feet "fingers*' 

 extended. Magnified about 1. From Agassiz. 



Earth-worms push their way through the soil by means of 

 small stiffened chitinous hairs called chaetae, which are ar- 

 ranged in pairs, so many to each segment. They can even 

 climb up almost perpendicular surfaces, provided that the 

 surface be rough. 



A great many animals swim. Fishes do that by the waggling 

 of their body, especially their tail, and the fins take a com- 



