A SPIDER 27 



The digestive system consists of a straight alimentary tube and 

 its many branches. In the cephalothorax, branches of it extend 

 to the legs, and a portion of it forms a sucking stomach, by 

 means of which the spider sucks up its fluid food. In the abdo- 

 men it becomes the intestine and gives off an extensive network 

 of tubules, which fills a large part of the abdomen and has the 

 appearance of a compact gland; its function, however, is not 

 secretory and it does not differ in structure from the rest of 

 the intestine. The end intestine possesses a large dorsal faecal 

 reservoir. 



The kidneys are a pair of branching Malpighian tubules. 



The brain lies just beneath the eyes. It is joined, by means of 

 broad connectives, with the large ventral ganglionic mass, from 

 which nerves extend into the abdomen and the appendages. 



The organs of respiration are the lungs and the tracheae. The 

 lungs are a pair of sacs which open to the outside through the 

 lung spiracles, each sac containing a series of lamellae, usually 

 called a lung-book, in which the blood circulates. The tracheae 

 open to the outside through the tracheal spiracle. 



The sexes are separate in spiders. In the male the testes are 

 a pair of tubular glands which are joined, by means of the coiled 

 sperm ducts, with the sperm vesicle, which opens to the outside 

 through the genital pore. The ovaries, in the female, are large 

 organs in the ventral portion of the abdomen, which are joined, 

 by means of the oviducts, with the uterus, which, after receiving 

 the paired receptacula seminis, opens to the outside through the 

 genital pore. 



The silk glands are branched or tubular structures in the 

 ventral portion of the abdomen. 



