288 LINN^US. 



VII. Aptera, Wingless. Insects destitute of wings in 

 both sexes. They are arranged under 14 genera^ and 

 consist of 300 species. In this order there are three divi- 

 sions : some have six feet, as the flea, the louse, and the 

 white ant ; others have from 8 to 14 feet, as the spider, 

 scorpion, crab, and lobster ; while others have a still 

 greater number, as the centipede. 



The generic characters are derived from the an- 

 tenna?, the jaws, the head, the thorax, the wings, 

 the elytra or wing-covers ; and the specific, from 

 the colours and other circumstances. The number 

 of species is 2984. 



The sixth class, that of Vermes or Worms, is a 

 very heterogeneous one, and to later authors has 

 supplied materials for several classes. Linnaeus di- 

 vides it into five orders : 



I. Intestina, Intestinal Animals : simple, naked, and 

 destitute of limbs : for example, the earth-worm, the 

 guinea- worm, the leech, and the ascaris : 7 genera, 24 

 species. 



II. MoLLUscA. Simple, naked animals, furnished with 

 limbs : the slug, the sea-mouse, the sea-anemone, the cut- 

 tle-fish, the sea-nettle, the star-fish, and the sea-urchin : 

 18 genera, 110 species. 



III. Testacea, Shell-fish. Soft, simple animals, co- 

 vered with a shell which is usually calcareous. This or- 

 der includes 36 genera, and 814 species. It is divided 

 into three groups, the multivalve shells, or those which 

 consist of several pieces ; the bivalve, of two pieces ; and 

 the univalve, or those of one piece only. 



IV. LiTHOPHYTA. Compound animals, aflixed to, and 

 fabricating a fixed calcareous base, called coral. There 

 are 59 species, which are referred to 4 genera, the tubi- 

 pores, madrepores, millepores, and cellepores. 



V. ZooPHYTA. Compound animals, sending forth pro- 



