178 SEGMENTED WORMS— THE ANNELIDS 



ductive process always takes place on the first day of the last quarter 

 of the October-November moon. At this time the surface of the water 

 near the shore may be filled with these swimming worm segments. 

 Natives of these regions have learned of this and gather these in large 

 numbers and have a feast. 



Parasitic Annelids — The Leeches 



"Tight as a leech" is an expression used to indicate a very high degree 

 of adhesion and any one that has tried to pull a leech off his body can 

 well appreciate how tight this can be. Leeches are another of the seg- 

 mented forms and have adapted themselves to a parasitic existence. 

 They do not live in the bodies of other animals like many of the flat- 

 worms and roundworms, but suck blood through the outer skin of their 

 hosts. Thus, they are ectoparasites rather than endoparasites like the 

 others. If you put a living leech in an aquarium it will attach itself by 

 a posterior sucker, and if you put your finger in the water it will stretch 

 and wave the anterior portion excitedly in an effort to reach the finger. 

 If it succeeds it will attach itself to your finger by the anterior sucker 

 and release its hold at the posterior. There are three sharp teeth on the 

 mouth within the anterior sucker and the skin is punctured by these 

 teeth which are so sharp that there is usually no pain at all. Then the 

 leech will gorge itself on blood, sucking in about three times its body 

 weight if undisturbed. It will then drop off in a stupor and will not 

 need to feed again for several months. 



The practice of medicine was, at one time, spoken of as "leechery" 

 because the doctors always carried a supply of large leeches in their little 

 black bags. There is one leech that is well adapted to their purposes 

 and it is still called the medical leech, Hirndo medicinalis. It is about four 

 inches long and capable of ingesting a considerable quantity of blood. 

 When a person was sick, it was believed that there was an upset balance 

 between the body fluids and, by removing some of the blood, the balance 

 could be restored and health would return. The leeches were a very 

 convenient method of accomplishing this, which accounted for their 

 popularity. More recently, the colorful barber shops of the early part 

 of the century kept a supply of leeches on hand and, when a man got a 

 black eye, or other conspicuous black and blue spots on his body, a lean 

 hungry leech was applied to the skin and the discolored blood was sucked 

 out. This practice has not entirely disappeared today, and it is possible 

 to buy these large medical leeches at some drug stores for this purpose. 



A particularly vicious land leech occurs in some densely vegetated 

 tropical regions where the rainfall and humidity of the air are great 



