CHAPTER III 



THE APPENDIOULATE PHYLUM 



IF we examine an ordinary Earthworm we may 

 at first be at a loss to understand how it is rightly 

 included in the Appendiculate phylum, since we can 

 at first detect no evidence of the presence of limbs. 

 But if the lower surface of the body is gently rubbed 

 with a finger, a certain roughness will be felt due to 

 the presence of groups of bristles partially embedded 

 in the body-wall of each segment. It is by means 

 of these bristles or setae that the worm obtains a 

 purchase on the earth for its movements, and they 

 indicate the degenerate remains of limbs. The marine 

 relations of the Earthworm, such as may sometimes 

 be seen swimming with graceful, sinuous movements 

 in rock-pools at low tide, possess much better de- 

 veloped limbs which project from the sides of the 

 body on each segment and are armed with longer 

 and more conspicuous bristles than those of the 

 Earthworm. All Annelids, then, possess limbs or 

 the rudiments of limbs, and in this respect they 

 resemble such animals as Centipedes, Insects, Spiders, 



