240 NATURAL HISTORY. 



length. They were the tubes of Ditrupa subulata, one of the Serpulines. This animal has two sets of 

 branchiae, rolled up spirally, and there are six fascicles of bristles on the body. The operculum is 

 concentrically striated. These worms live at considerable depths, and the coral Caryophyllia borealis 

 grows upon them. More Serpuline-looking, but very slender thread-like shining tubes in masses, are 

 often found below low spring-tide mark in Devonshire, and they belong to the genus Filograna. 



The genus Spirorbis is very familiar to folk that pick up the long seaweed on British coasts. 

 On it there are small, flat, spiral, or twisted shells, with at least three turns. It is a tube formed of 

 carbonate of lime, and is attached by one surface entirely. When living, this tube contains a little 

 worm which projects its filamentary branchiae at one end, and which has one or two trap-doors 

 or opercula. The young undergo a kind of incubation within the tube, in a process or pouch, within 

 the body of the parent. 



THE SUB-CLASS HIRUDINEA.-THE LEECHES OR SUCTORIAL ANNELIDA. 



Formerly, nearly everybody was familiar with the appearance of a Leech, for one or more were 

 frequently ordered to be applied to tender and inflamed parts of the body by medical men. But now 

 that blood-letting is not required to be done so frequently, the Leech is really very rarely seen. Some 

 persons who sell Leeches keep them in darkness, and crowd a multitude together ; but more 

 reasonable people keep a few in a fresh-water aquarium with a secure top. There the Leeches may 

 be seen, occasionally swimming with an undulatory up-and-down movement, and they then look flat, 

 long, and rather pointed at both ends. When they come to rest at the bottom or fix on to the 

 sides of the glass, their shape alters, and they become shorter, thicker, and more cylindrical, retaining, 

 however, some flatness at the under part, and a narrowing fore and aft. But it will soon be observed 

 that there is a flat disc on each narrow end, or head and tail, and that it can be applied 

 to the substance on which the Leech is moving or resting, so as to fix the body as if it were a sucker. 

 There are neither legs nor feelers, and the outside of the body is covered with rings, one behind 

 the other, and from 95 to 100 in number. The colour of the Medicinal Leech is greenish-olive or 

 very dark green, with six yellow-reddish or yellow bands along the back, and the belly is yellowish- 

 green with black spots. 



On taking one out of the water, it will diminish much in size, and will contract, become much 

 harder, and swollen in the middle, and on permitting it to i-est 011 the hand it will after a while 

 begin to fix the front sucker to the skin, and then a sharpish prick or series of pricks is felt, and the 

 Leech begins to elongate and to move its body in a slightly undulatory manner. After some minutes 

 the body begins to swell, and the front sucker is well fixed, and the part immediately behind it is 

 narrowed, the rest of the body being plump. After a time the Leech becomes many times its usual 

 thickness, and it suddenly lets go its hold, falls off, and some blood conies from the spot on which the 

 sucker had fixed, as well as from the mouth of the Leech, which is then seen to be at the bottom of the 

 sucker. It has removed a certain quantity of blood from the hand, and the wound has been made by 

 three jaws disposed in a triangle, and having their fine, curved edges toothed. The suckers act by 

 their muscular fibres clasping the surface and expelling the air or water, and this brings the jaws 

 in contact with the surface, and each is moved backwards and forwards, the teeth being downwards 

 and the fixed point upwards. The result is three wounds, each radiating from a common point. 



In their early life the Leeches fix on to the larvae of insects in the water and suck them, and 

 after more growth, fishes and frogs are attacked and have their blood sucked. The Leeches then 

 frequently leave the water and wander in damp places, and if they have the opportunity, they creep 

 on to the skin of warm-blooded animals and gorge themselves. Their sucking is followed by a 

 prolonged fast, and indeed it is very wonderful how long some Leeches will live without food. Possibly 

 from six months to two years are occupied in the process of digestion. Leeches grow very slowly, and 

 some years elapse before they arrive at maturity, and they are not fit for medicinal purposes before 

 the age of a year or eighteen months. There are, according to Cobbold, three species of leeches used 

 in medicine, the Grey*, Green t, or Dragon J Leech. When it was the fashion to vise Leeches in the 

 olden time, the medical man himself had the compliment of being called a ''Leech" a term 

 appropriate enough so far as healing is concerned, but singularly inappropriate in all other respects, 

 * Hirudo medicinalis. f Hirudo ojficiiialus. J Hirudo interru-pta. 



