228 THE ANIMAL KINGDOM. 



shortened or elongated by the muscles which draw together 

 the rings (these are placed longitudinally), or by those which 

 contract and widen them, placed circularly ; this enables 

 them to move along, and in so peculiar a manner that it has 

 received the name of " vermicular," or worm-like. The most 

 familiar example of this class is the Earth-worm (Lumbricus 

 terrestris), this lowly creature lives in soft mud and clay 

 and bores its way into the ground, in doing so it is assisted 

 by a slimy secretion which covers it, its food consists of earth 

 containing organic matter, this it swallows constantly and 

 extracts what is fit for its nourishment ejecting the remainder 

 apparently unaltered ; the curious little heaps of soft dirt 

 which are so often seen in wet weather on the garden-paths, 

 &c., are formed in this way. The Leech is another familiar 

 example of the Annellata or Annelidas, this little useful 

 creature lives in ponds and stagnant waters, and feeds by 

 sucking the fluids of other animals (chiefly frogs and fish) 

 with which it will gorge itself till it is double its original 

 size, it will then remain (often for months) without food 

 till it is all appropriated, the process going on very slowly ; 

 a full-grown Leech is perhaps twenty years old, they grow 

 so slowly, (hence it is, that Leeches may be kept for months 

 after being gorged with blood without any food, and they 

 will live and be healthy). They are furnished with two 

 suckers, one at each end, and a mouth with numerous fine 

 teeth placed in a tri-radiate manner, with which they pierce 

 the skin when about to feed. They move in the water with 

 great rapidity by a wavy motion of their bodies, but on solid 

 substances their mode of progression is that of adhering by 

 the sucker in front, then drawing the other one close up and 

 extending the body to its full length, taking hold again by 

 the front sucker and again bringing up the hindermost. 



The Cirripeda constitute the second class of the Articulata, 

 which comprise the " Acorn shells " and " Barnacles" (fig. 14); 

 these little creatures were formerly described as Molluscs, 

 but are now considered to be articulate animals, and by some 

 as Crustaceans. Dr. Baird gives the following description of 

 them: "The Cirripeds are articulated animals contained 

 within a hard covering composed of several pieces and con- 



