618 



ZOOLOGY 



SECT. 



more 



appendages which probably carried the 



ceph 



cfterc 



rounding the mouth, and, with the exception of the first, toothed 

 at the bases in order to perform the functions of jaws : the last 

 pair are stouter than the others and are expanded so as, apparently, 

 to assume the character of swimming paddles. Certain of the 

 anterior of the free segments bear paired lamelliform 



branchiae as in the 

 Xiphosura. The exo- 

 skeleton is in many 

 cases elaborately 

 sculptured. 



A cartilaginous in- 

 ternal endosternite 

 of the same nature 

 as that which has 

 been described as oc- 

 curring in the Scor- 

 pions is found in 

 Limulus and in cer- 

 tain Spiders, but 

 not in the other 

 groups. 



Coxal glands, 

 similar to those that 

 have been described 

 in the Scorpion, oc- 

 cur also in most 

 Spiders, in the Sol- 

 pugida and Phalan- 

 gida, in some Acarida 

 and the Xiphosura. 

 In the Solpugida and 

 Phalangida they oc- 

 cur on the bases of 

 the last pair of legs ; 

 in the Araneida and 

 Xiphosura, as in the 

 Scorpion, they are 

 found on the bases 

 of the fifth pair of 

 appendages. 



Alimentary system. The oesophagus (Fig. 513, o>s.} of the 

 Spiders is expanded behind into a special sucking stomach (suck. st.}. 

 The inesenteron (i/tcsi'nt.) gives off in the cephalothorax five pairs 

 of narrow divrrticula (arc.) which enter the bases of the pedipalps 

 and legs : in the abdomen it also gives off a number of caeca, which 

 branch and come in close relation with a mass of cells commonly 

 termed liirr (luy.), though not known to have the function of that 



Fi<;. ."ill. Ventral view of Iiimulus. 1 (i, appendages of 

 cephalothorax ; '/. abdomen ; ccph. cephalothorax ; operc. 

 operculum, behind which are seen the series of abdominal 

 es ; tJ*. caudal spine or telson. (After Leuckart.) 



