230 



ANNELIDA. 



whole animal a movement that not only pre- 

 pares the creature for advancing further into 

 the soil, but, by swelling out the anterior seg- 

 ments, forcibly dilates 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, 

 preventing any retrograde movement, the head 

 is again forced forward through the yielding 

 mould, so that, by a repetition of the process, 

 the animal is able to advance with the greatest 

 apparent ease through substances which it would 

 at first seem utterly impossible for so helpless 

 a being to penetrate. 



(598.) 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 by 

 the older physiologists these creatures were re- 

 garded as aifording 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 stomach ; so that the 

 exception to the general law of nature sup- 

 posed to exist in the Earthworm has no founda- 

 tion in truth. The whole intestinal tract of 

 one of these animals is represented in fig. Ill : 

 it consists of a wide oesophagus which termi- 

 nates in a crop-like dilatation ; to this succeeds 

 a muscular gizzard (fc), and a long sacculated 

 intestine (I I) that passes in a direct line to 

 the anus. 



(599.) In the Earthworm, says Dr. Williams, 

 the chylaqueous fluid is almost entirely sup- 

 pressed, and the visceral cavity obliterated. 

 This vulgar worm, however, does not breathe on 

 .the atmospheric, but on the aquatic principle. 

 It dies rapidly in perfectly dry places. Its cu- 



Fig. 111. 



Viscera of the Earth <.nn. 



