INSECTS ANNELIDA DIAGRAM G. 155 



CLASS ANNELIDA. 



The elass Annelida is composed of soft animals formed of 

 numerous segments, which have no limbs. The leech and earth- 

 worm are annelides. These animals are remarkable for their red 

 blood. If we look at the back of a small earth-worm, we see a red 

 filament under the skin. On carefully observing it, we notice that 

 it is sometimes broader and sometimes narrower, and that the 

 slight dilation which it momentarily exhibits, passes along through 

 the whole length of the animal, from back to front. The vessel 

 which exhibits these pulsations is the heart. 



The Earth-worm, like other annelides, has no limbs, but if we 

 look closely at a large one, and especially when we take it in the 

 hand, we see that a great number of short stiff hairs issue from 

 its belly, with which it crawls. It is for this reason that it is so 

 difficult to pull an earth-worm out of its hole when it is partly in 

 it, as it takes hold of the sides of its dwelling with this kind of 

 grapnels. A little in front of the middle of its body, the earth- 

 worm has a swelling, which is called the corslet. If an earth- 

 worm is divided behind the corslet, the anterior portion does not 

 die, and reproduces a tail ; the worm becomes exactly similar to 

 what it was before. Worms feed by swallowing earth. It must 

 not, however, be supposed that this would nourish it ; but there is 

 always a large quantity of animal and vegetable refuse in the 

 ground ; it is these matters which are digested, and which form 



