a degenerate, specialized and unappealing animal. To appreciate segmented 

 worms properly one must see their marine relatives, which have retained definite 

 heads, often with biting or pinching jaws and sometimes a shock of ''hair'' or 

 tentacles, and along whose sides are rows of paddlc'like structures, called para' 

 podia, serving as both legs and gills. The heads of the land and fresh-water 

 forms are almost non-existent and the parapodia are represented only by tiny 

 bristles or setae, which aid the worms in their movements or enable them to 

 resist the tug of the early bird. The only external character at all noticeable in 

 the adult earthworm is the clitellum, a thickened area somewhere between the 

 twelfth and the thirty-fifth segments. 



Sexual activity usually begins after the first warm rains of spring and 

 continues through the summer. In the evening, when earthworms mate, each 

 worm emerges from the ground so far that only the tip of its tail remains in 

 its burrow. Then it moves around in search of a neighbor. If it succeeds in 

 finding one, the two lie side by side, head towards tail, and a secretion from the 

 clitellum of each forms a belt around the two. Then, since each worm is both 

 male and female, the two exchange sperm and finally separate. Later the clitel- 

 lum again becomes active, secreting another belt, this time around the one worm. 

 The worm deposits some of its eggs and some of the sperm it received from its 

 neighbor within this secretion of the clitellum. It then backs out of this belt, 

 which closes down on eggs and sperm like a section of elastic tubing and forms 

 the cocoon in which the young worms develop. 



The small aquatic annelids usually have long setae or bristles projecting 

 from the body and so are commonly called Bristle Worms. It is necessary to 

 make out the details of these bristles in order to identify these worms, and some 

 difficulty is caused by the fact that some of the bristles may be retractable. A 

 weak solution of glycerine as a mounting fluid is helpful in slowing down the 

 activities of a worm and enabling one to study it from all sides. Some of the 

 aquatic annelids reproduce sexually. Others reproduce by fission. A constric- 

 tion appears in the mid-region of the body, a head develops behind this con- 

 striction, and soon two worms appear in place of one. 



The part worms play in human affairs, aside from those of the fisherman, 

 is seldom appreciated. Charles Darwin's book. The Formation of Vegetable 

 Mould, Through the Actiori of 'Worms, is a revelation to most readers and 

 gives astounding facts on the immense worm population of fields, the utility of 

 worms in maintaining soil fertility, and even their value to the archaeologist in 

 preserving the ruins of antiquity. 



Leeches or blood suckers are common in most ponds and streams but, 

 fortunately for our peace of mind, few of them seek human blood. Some of 

 them are not even parasitic, but feed on small animals and plant material. They 

 may be distinguished from all other aquatic animals by their sucking discs, one 

 at each end; by their appearance of extreme segmentation, since each somite 



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