670 



THE EARTH-WORM AND THE LEECH. 



and-white splendor, a hand moved between it and the window will 

 cause it to disappear into its tube with a movement so rapid that the 

 eye cannot follow it. The gills, whose exquisitely graceful form and 

 delicate coloring have always attracted admiration, are affixed to the 

 neck, as, if they were set at the opposite extremity of the body or 

 along the sides, they would not obtain sufficient air from the small 

 amount of water that could be contained in the tube. The beautiful 

 scarlet stopper ought also to be mentioned. Each set of gills is fur- 

 nished with a tentacle-like appendage, one of which is small and 

 thread-like, and the other expanded at its extremity into a conical 

 operculum or stopper, marked with a number of ridges, which form a 

 beautiful series of teeth around its circumference. The footstalk on 

 which this stopper is mounted is a little longer than the gills, so that 

 when the animal retreats into its tube the gills collapse and vanish, 

 and the entrance of the tube is exactly closed by the conical stopper. 

 The family of which the common Earth-worm is a very familiar 

 example is distinguished by the ringed body without any gills or 

 feet, but with bristles arranged upon the rings for the purpose of 

 progression. 



In the well-known Earth-worm the bristles are short and very stiff, 

 and are eight in number on each ring, two pairs being placed on each 



side; so that, in fact, there are 

 eight longitudinal rows of bristles 

 on the body, four on the sides and 

 four below, which enable the crea- 

 ture to take a firm hold of the 

 ground as it proceeds. Except 

 that the worm makes use of 

 bristles, and the snake of the 

 edges of its scales, the mode of 

 progress is much the same in both 

 The whole body of the creature is very elastic, and capable of 

 being extended or contracted to a wonderful degree. AVhen it wishes 

 to advance it pushes forward its body, permits the bristles to hitch 

 against the ground, and then, by contracting the rings together, brings 

 itself forward, and is ready for another step. As in each full-grown 

 Earth-worm there are at least one hundred and twenty rings, and each 

 rmg contains eight bristles, it may be imagined that the hold upon the 

 ground is very strong. 



The Common Leech is almost as familiar as the earth-worm, and is 

 one of a genus which furnishes the blood-sucking creatures which are 

 so largely used in surgery. It belongs to a large group of Annelida 

 which have no projecting bristles to help them onward, and are there- 

 tore forced to proceed in a different manner. All these Leeches are 



The Common Leech {Hirudo medici- 

 ncdis). 



cases. 



