BRINE-SHRIMP— WORMS — LEE CUES 



377 



Worms. 



Worms are naturally numerous in the vicinity of water. In 

 the sparsely bristled group we have a species known as Rhynckelm is 

 Umosdla. which lives in muddy ditches, and is of a light purple colour, with a long, 

 thin, thread-like bristle on the head : it is flat and angular on the back, and almost 

 square in form. The tube-worms are also inhabitants of the muddy bottoms of 

 ditches, where they live with the fore end of the body stuck into the mud, while 

 the hind part protrudes, and is in a constant state of vibration. Of these the brook- 

 worm {Tiibifex rividorum) is often seen in thousands forming red patches on the 

 river-bottom, which disappear at once if stirred with a stick or trodden upon ; the 

 worms, which are 1 or 2 inches long, and have a pair of barely visible bristles, retir- 

 ing into their mud-tubes, to reappear after an interval. Another worm, the beaked 

 nais (]\ r ais proboseidea), unlike the two last, does not live in a tube but on aquatic 

 plants. It is about half an inch long, with the head terminating in a long, thread- 

 like prolongation, and furnished 

 with two e3^es : the body being 

 transparent and slightly jointed, 

 with four longitudinal rows of 

 bristles. Nearly allied is the snake- 

 nais (JY. serpentina), of rather larger 

 dimensions, and without the pro- 

 longation, but with two eyes, and 

 three or four blackish transverse 

 bars on the head. These worms, 

 which appear to the unaided eye 

 as twisting threads, do not as a rule 

 propagate by eggs but by spontan- 

 eous self-division. 



In another group we have 

 Dendrocoehnn lacteum, about an 

 inch long, wdiich has black eyes 

 with an intestine showing violet 

 through the skin, and the body 

 pointed at the back. Common in 

 ditches, where it creeps about 



dragging its body along in jerks, it is tenacious of life, and when cut in pieces 

 joins itself again, even the sucking-tube being capable of performing its function 

 when severed from the other parts. With the worms are often classed the wheel- 

 animalcules, or Rotifera, which appear in such numbers in the height of summer 

 that they form milky coverings to aquatic plants. Nearly all subsist on small 

 animals and plants, which they sweep into their mouths by the movements of the 

 fine hairs, or cilia, on the wheel-like disk. 



Representing another class (Hirudinea) are the well-known 

 leeches, of which the most remarkable is the common Hirudo rnedi- 

 cinalis, once used so largely in medical practice, whose life-history has been so 

 frequently given at length that it need not be repeated on this occasion. 



Another familiar member of the group is the horse-leech (Aidostoma gido), 



THE LEECH. 



Leeches. 



