The Internal Anatomy of Spiders 



simple caeca; but in the abdomen they are much-branched tubules, 

 forming a great mass, which has the general appearance of a 

 gland. These diverticula may be designated as follows: 



The anterior cceca. — At the beginning of the mid-intestine 

 a caecum extends forward on each side of the dorsal muscle 

 of the sucking stomach (Fig. 163 ac). These two caeca 

 often unite in front of this muscle, thus forming what has 



been termed the ring- 

 stomach, or the ccecal ring. 

 The lateral cceca. — 

 From each anterior cae- 

 cum, four lateral caeca 

 arise. These extend later- 

 ally and ventrally and 

 each ends in or near a coxa 

 of a leg (Fig. 163, Ic). 



The alimentary tubules. 

 — In the anterior part of 

 the abdomen, there arise, 

 from a somewhat ex- 

 panded portion of the 

 mid-intestine, several 

 much-branched dorsal di- 

 verticula; these constitute 

 the alimentary tubules. 

 These are developed to 

 such an extent that they 

 form the most prominent 

 part of the viscera of the 

 abdomen. 



The mass of alimen- 

 tary tubules was described by the early writers as the liver and 

 by later ones as a digestive gland; but it has been shown that 

 the epithelium of these tubules does not differ from that of the 

 main portion of the mid-intestine; and that the food penetrates 

 to the tips of the tubules and is absorbed by the tubules. 



C THE HIND-INTESTINE 



The hind-intestine is the terminal portion of the alimentary 

 canal; it is that part that is developed from an infolding of the 



156 



Fig. 163. DORSAL VIEW 

 OF THE CEPHALOTHORACIC PORTION OF THE 



ALIMENTARY CANAL 



0, oesophagus s, sucking-stomach ac, anterior caeca, 



united in front Ic, lateral caeca (after Leuckart) 



