THE EARTHWORM . 11 



trial existence^ the locomotive members and other 

 portions of the swimming-worms are constructed in 

 conformity with their marine life*. 



The Annelida, or annulose worms^ then, the highest 

 and most perfect of the four orders, contain amongst 

 their number the Earthworm {Lumbricus terrestris), 

 which, in common with its congeners, possesses, as 

 you well know, a sofb elongated body. This, in the 

 full-grown animal, is usually divided into from 120 

 to 150 rings or segments, which decrease in circum- 

 ference as they approach either end, causing the body 

 to terminate in what may be called two pointed extre- 

 mities, the head and the tail. To the hooks, situated 

 upon each ring of the body, we have already alluded 

 in our Introduction, and these are the only append- 

 ages that the worm possesses (see section of Worm's 

 body, PL II. fig. 4). But you wiU perhaps be some- 

 what surprised to hear us speak of the "head" of 

 a worm, for you are accustomed to connect with that 

 idea a mouth, eyes, nose, and ears, none of which 

 are perceptible in the worm ; and the first, that is the 

 mouth only, being actually present. Although, how- 

 ever, the senses of vision, smell, and hearing are, so 

 far as we have been able to ascertain, denied to this 

 humble AnneMe, yet we cannot but grant to its 

 anterior final ring the title of a head ; for if you exa- 

 mine it with a pocket-lens, whilst the creature raises 

 that part of its body, you wiU perceive upon it a 

 * See note, page 27, Letter IV. 



