414 ZOOLOGY 



and posterior. The rays are each continued into nerves ; of 

 these the first pair is continuous with the circum-oesophageal 

 commissures, the second supplies the pedipalpi ; the next four 

 stout rays supply the four legs, and the posterior pair is con- 

 tinued back into the abdomen, the two nerves lying so close 

 together as to be often mistaken for one. 



The sense organs of spiders are limited to eyes which are 

 always simple, and to taste organs. The number and arrange- 

 ment of the eyes are of great use in classification, the various 

 families having a different and definite arrangement of these 

 organs. In Upeira the visual organs are situated on the 

 anterior part of the cephalothorax ; there are four large eyes 

 arranged c[uadrilaterally, and on each side of the square are two 

 smaller eyes, the members of each pair being connected by a 

 ridge of chitin. 



The male, as is usually the case in spiders, is smaller than 

 the female, and whilst the latter usually sits in the centre of 

 the circular web, the male is to be found hidden under the leaves 

 of a neighbouring bush. 



The ovary is situated in the abdomen ; it lies ventrally, 

 and is surrounded by the caeca of the liver and spinning-glands. 

 It consists of two hollow tubes which unite posteriorly, and 

 are continued backward as a thread ; anteriorly each ovary is 

 continuous with an oviduct; during the breeding season the 

 ovaries are much swollen, and the ova form projections on the 

 walls of the organ (Fig. 236). The oviducts open into a uterus, 

 and this opens into a recess on the ventral wall of the 

 abdomen. The external genital armature of the female is 

 called the epigynium ; it is often of a very complex character, 

 and its nature is of considerable use in determining the species 

 of a spider. In addition to the opening of the oviducts, it 

 also receives the external ducts of the two spermathecae ; these 

 ducts may be short and wide, or long and coUed. There are 

 also a pair of internal ducts which lead from the spermathecae 

 to the oviduct, and along which the spermatozoa pass to 

 fertilise the ova before they are laid. The epigynium is 

 rendered more complex by the presence of numerous structures 

 which serve to guide the palpal organs of the male into the 

 external openings of the spermathecae; it only exists in its 



