t 175 ] ii8 



another by an hexagonal or six-sided figure, and placed in the most 

 exact order. Leewenhoek counted thirty-five of these lenses on the 

 fourth part of the sphere of one eye; the entire circumference will 

 therefore contain 140; hence, he sa3's, it follows, that each eye is com- 

 posed of 3,000 optical organs; but, if both parts together constituted 

 a sphere, tlicy then contain 6,236. When the eye is separated and 

 made clear, these hexagons are as transparent as crystal. Leewen- 

 hoek having properly prepared and fitted an eye to a microscope, 

 couLd sec through it clearly, but the largest objects viewed, were di- 

 minished to an incredibly small size. The steeple of the church in 

 Delft, which is 300 feet high, at 750 feet distance, appeared no larger 

 than the point of a needle, seen by the naked eye. 



Not hup^e Behemoth, nor tlie whale's vast form, 

 That spouts a torrent, and that breathes a storm, 

 Transcends in organs apt this puny fly, 

 Set with ten thousand lenses." — Evans. 



The construction of these compound eyes, is admirably adapted to the 

 convenience of the insect; for, as they are immovable, they would 

 have lost sight of many objects, if their eyes had been framed like 

 those of other animals; but, by their form, they can easily see sur- 

 rounding objects. As we do not see double with our eyes, so the numer^ 

 ous inlets to sight in an insect, may increase their field of view. 



When the v/orm is first hatched, it is very minute, and of a brown 

 hue, if healthy. This luie is derived from the hairs covering its bo- 

 dy: they disappear in the course of a few days, when it assumes a 

 light or dark hue, according to the nature of the particular variety. 

 Behind the head, the skin is formed into six wrinkles. The body is 

 composed of twelve articulations, or rings: each ring, except the se- 

 cond, tliird, and lost, is marked on the sides, and near the belly, with 

 spots of a deeper color than that of the skin, and show oval openings 

 through which the insect respires. These openings are termed spira- 

 cula,t or breathing holes, and communicate, internally, with two air 

 vessels, running the whole length of the body, one on each side, in a 

 straight line, from one spiracle, or stigma, to another, and, uniting 

 near the head, form one trunk. They serve, or perform, the office of 

 lungs. In other wonls, these stigmata are eighteen mouths, which 

 admit air into the principal air vessels in the large trunks of the tra- 

 chea, or wind-pipes, whence it is led to the diflerent and nunierous ra- 

 mifications of the air tubes, to the intestinal canal, to the other inter- 

 nal parts, and to the skin. 



* The numher of lenses in an eye, varies in diflerent insects. Leewenhoek coimt- 

 ed 8,000 in that of a common house fly. CaJ Hooke fbj computed 7,000 in a horsti 

 fly; and Pug-et fcj 17,325 in that of a butterfly. 



f Malphigi and Reaumur call them stig'oiata. 



(aj Select works, 4to. vol. \. p. fi2. Lnnl. 1790. (,l/) Jlir-ograpliia, p. ITS, 



fc) Amaenitates Acailt-micie. vol. X p. 14J. 



