80 



thexs, as in birds; in others, they are covered,, or en* 

 closed incases. -In many sgecies, the male is winged^, 

 smd the femqle not. 



On the sides, or extremities of the body, are little 

 oval apertures, shaped like the ball of the eye, arid sus- 

 ceptible of the same motions. These are so many 

 moutns, for the purpose of respiration.. 



l6. The interior. part of insects contains four princi- 

 pal viscera; the spinal marrow, the intestinal* bag, the 

 heart, and, the tracheal arteries. 



A blackish thread, which is extended the whole, 

 length of the belly, from the head to the hinder part, 

 and knit together at certain distances, is the spinal mar- 

 row of inserts, or the principal trunk of the nerves. 



The knots placed from one space to another, seem so 

 many particular brains, appointed to distribute the ner- 

 vous strings to the neighbouring parts ; from the action, 

 of which the feeling and motion proceed. The first of 

 these knots constitutes the brain, properly so called. 



On the medullary thread is placed the intestinal lag, 

 which is equal to it in length. It is a long gut, in 

 which are contained the oesophagus, the stomach, and' 

 intestines, 



Along the bag, and parallel to the iotestin.al bag, 

 there runs a long and thin vessel, in which may be per- 

 ceived, through j he skin of the insect, alternate contrac- 

 tions and, dilatjons. This is the heart, or that part 

 which performs the functions of it. 



The arterial vessels of insects perfectly resemble those 

 of plants. There is in every part of them the same 

 structure, colour, elasticity, destination, and dispersion, 

 through the whole body. 



37 Worms, whose bodies are lodged "irt a crusta- 

 ceans, or stony pipe, seem to constitute ti 

 fcstween insects ahd shell-fish, 



