288 ARTICULATA. 



Several of them form their eggs into a cocoon, and envelop them with 

 a fibrous excretion. 



They have been subdivided from characters principally drawn from the 

 organs of their mouth. In the 



SANGUISUGA, Savigny, 



Or, the Leech, properly so called, the superior lip of the anterior cup or 

 sucker is divided into several segments; the aperture is transverse and con- 

 tains three jaws, each edge of which is armed with two rows of very fine teeth, 

 which enable it to penetrate through the skin without causing a dangerous 

 wound. It is marked with ten small points, considered as eyes. 



We all know the medicinal or Common Leech Hirudo medicinalis, Lin., 

 that useful instrument for the local abstraction of blood. It is usually blackish, 

 with yellowish streaks above, and yellowish with black spots beneath. It is 

 found in all stagnant waters. The remaining divisions are Hatmopsis (The 

 Horse Leech), Bdella, Nephelis, &c. &c. 



GORDIUS, Linnaeus. 



The body resembling a thread, the only mark of the articulations being 

 slight, transverse plicae ; it has neither feet, branchiae, nor tentacula. Inter- 

 nally, however, a nervous system is perceptible in a knotted cord. Perhaps 

 it will be necessary in the end to place them among the cavitary Intestina, 

 like the Nemertes. 



They live in fresh water, in the mud, and in inundated grounds which they 

 perforate in every direction. 



The different species are not yet well distinguished ; the most common, 

 Gordius aquaticus, Lin., is several inches in length, almost as fine as a hair, 

 and brown, with blackish extremities. 



CRUSTACEA, ARACHNIDES, AND INSECTA: 



OR ARTICULATED ANIMALS WITH ARTICULATED FEET. 



These last three classes of the Articulata, which were united by 

 Linnaeus under the general name of Insecla, are distinguished by at 

 least six articulated feet. Each articulation is tubular, and contains 

 the muscles of the succeeding one, which always moves by ginglymus, 

 that is, in but one direction. 



The first articulation, which attaches the foot to the body, and which 

 is composed -of two pieces, is called the coxa, or hip; the following one, 

 which is, usually, nearly in a horizontal position, the femur, or thigh; 

 and the third, generally vertical, the tibia or leg. To these ensues a 



