A spider’s body consists of two parts, a cephalothorax (head + thorax) and an abdomen. There is a waist, but no neck. The eight legs are attached to the cephalothorax, and the abdomen is not segmented or ringed like that of an insect, but entire, and bears at its extremity or on its under surface a little group of spinnerets or finger-like projections from which the spider’s silk proceeds. For the moment these three characteristics will suffice—the “waist” behind the leg-bearing portion of the body, the unsegmented, legless, abdomen, and the spinnerets (fig. 1 _B_). A harvestman, for instance, lacks the waist, and its abdomen is segmented. Mites are of very varied form and in some the body is more or less divided into two portions, but at least two pairs of legs will be found to be attached to the hinder portion; and neither harvestmen nor mites possess the spinnerets which are the most striking characteristic of the spider; some mites—like the “red spider”—can spin, but the mechanism by which that operation is performed is of quite a different nature. [Illustration: Fig. 1. _A_, a Mite; _B_, a Spider; _C_, a Phalangid.] Having, then, very readily determined our specimen to be a true spider, we may as well use it to note some further structural points the detailed examination of which may be deferred till we have considered their functions. Note the jaws or _chelicerae_, consisting of a stout basal part and a fang which, when not in use, is shut down like the blade of a knife; note the pedipalps or feelers, exactly like small legs, but showing by their action that their function is sensory and not locomotor. If they are knobbed at the end, the specimen is a male, otherwise it is a female or as yet immature. Look closely at the front part of the cephalothorax, and several eyes will be visible—probably eight. They are not compound—divided into innumerable facets, like those of insects—but simple and smooth, though to make sure of this the use of a microscope would be necessary. Finally, obtain a view of the under surface of the abdomen, and note in front, on either side of the middle line, two semilunar patches of a lighter colour. These are the “lung-books,”—special breathing organs peculiar to these animals; two is the usual number, though certain spiders possess a second pair behind the first.