ARTICULATA. 279 
their soft, unjointed abdomen, separated from the thorax 
by a narrow constriction, and provided at the posterior 
end with two or three pairs of appendages, called “ spin- 
nerets,” which are considered homologous with the legs. 
The office of the spinnerets is to reel out the silk from the 
silk-glands, the tip being perforated by a myriad of little 
Fig. 252.—A, female Spider; B, male of same species; C, arrangement of the eyes. 
tubes, through which the silk escapes in excessively fine 
threads. An ordinary thread, just visible to the naked 
eye, is the union of a thousand or more of these delicate 
streams of silk." These primary threads are drawn out 
and united by the hind legs. 
The mandibles are vertical, and end in a powerful hook, 
in the end of which opens a duct from a poison-gland in 
the head. The maxillee, or “palpi,” which in Scorpions 
are changed to formidable claws, in Spiders resemble the 
thoracic feet, and are often mistaken fora fifth pair. The 
