ANNELIDA. 



niiated between the particles of the earth, 

 which, from their conical shape, they pene- 

 trate like a sharp wedge ; in this position 

 they are firmly retained by the numerous 

 recurved spines appended to the different 

 segments : the hinder parts of the body are 

 then drawn forwards by a longitudinal con- 

 traction of the whole animal ; a movement 

 which not only prepares the creature for 

 advancing further into the soil, but by swell- 

 ing out the anterior segments forcibly di- 

 lates the passage into which the head had 

 been already thrust : the spines upon the 

 hinder rings then take a firm hold upon the 

 sides of the hole thus formed, and, prevent- 

 ing any retrograde movement, the head is 

 again forced forward through the yielding 

 mould, so that, by a repetition of the pro- 

 cess, the animal is able to advance with the 

 greatest apparent ease through substances 

 which it would at first seem utterly impossi- 

 ble for so helpless a being to penetrate. 



(246.) The alimentary canal of the earth- 

 worm is straight and very capacious. Its great 

 size, indeed, is in accordance with the nature 

 of the materials employed as food, for it is 

 generally found distended with earth ; and, 

 indeed, by the older physiologists these 

 creatures were generally regarded as afford- 

 ing proof that the nourishment of animals 

 was not exclusively derived from animal and 

 vegetable substances, since in this case they 

 supposed nutriment to be obtained from 

 matter belonging to the mineral kingdom. 

 This supposition, however, has been long 

 since exploded, for it is not from the earth 

 that nourishment is afforded, but from the 

 decaying animal and vegetable particles 

 mixed up with the soil taken into the sto- 

 mach ; so that the exception to the general 

 law of nature supposed to exist in the earth- 



Fig. 





