VOL. XXXVI.] PHILOSOPHICAL TRANSACTIOXS. 425 



an acorn, with the mouth a little contracted. The head e, which is the smaller 

 end of this worm, has a hollow body underneath, of a conical, or almost 

 hemispherical form, which seems to serve it for a mouth to suck, as well as to 

 fasten itself on the various bodies that come in its way, after the manner of 

 other leeches. 



The belly b is of a dark colour, because several viscera, contained in it, are 

 filled with a thick, black liquor; which makes it look as if the skin was of that 

 colour. The fore part ce is variously shaped, according to its different motions; 

 sometimes it prolongs itself, and then it becomes slender ; the diminution be- 

 ing made gradually up to the head ; and sometimes it contracts itself, and then 

 the thickness increasing, it becomes equally so throughout. The hinder part 

 CB does not change its figure, because it moves but slowly, and very seldom. 

 The motion of the fore part is of 3 sorts ; prolongation, contraction, and the 

 making itself round on all sides. The protuberance also is endued with two 

 motions, extension and undulation, which is made from the centre to the cir- 

 cumference. When this insect stops itself any where, it holds firmly by means 

 of this protuberance. Before applying this, it shortens it, by withdrawing the 

 edges, or the circumference towards its centre ; and after applying the orifice 

 of its protuberance on the surface of any body, it lifts up a little the centre or 

 bottom, towards its own body ; afterwards it swells, and stretches it on all sides, 

 according to all its dimensions. This protuberance thus applied, stretched and 

 void of air, makes that which endeavours to enter, press it externally on all 

 sides, and holds it so fast, that it is above the strength of the animal to separate 

 it from its place where it is applied. The animal being thus fastened, and de- 

 tained by its protuberance, its fore part is always in motion, while its hinder 

 part remains almost immoveable. It stretches its head sometimes to the right 

 hand, sometimes to the left, by lengthening and shortening its fore part, which 

 bends and straightens itself very frequently. The extent of all these motions is 

 marked by pricked circles of diff'erent sizes, touching each other at one point of 

 their circumference, at the centre of the protuberance, which is as it were the 

 beginning and fixed point of all these motions. By these difterent motions the 

 insect performs the two functions necessary to it. When the little animal wants 

 to change its place, it makes use of its protuberance <ind its sucker, which is 

 the little hollow under its head, and seems to serve it for a mouth : it applies 

 this part to the place d, whither it would remove its body, and after being pro- 

 longed by its fore part to reach the place, where this application should be 

 made, it draws its protuberance and sucker together, by bending its fore part 

 circularly, after the manner of some caterpillars. Its protuberance being applied, 

 it loosens its sucker, and prolonging itself, applies it to another place more for- 



VOL. VII. 3 I 



