PROBOSCIS ALIMENTARY SYSTEM 



515 



In some cases, where the proboscis itself is short, as in 

 Pallene, this mechanism is carried backwards into the fore-part 

 of the body ; and, in the latter genus, the narrow oesophagus 



-RetM 



Fig. 278. — Transverse sections through the proboscis of Ph. charyhdaeiis. A, Anterior, 

 through the principal ganglionic mass {G) ; B, posterior, at the level of' the sieve- 

 hairs (h). Coec, Intestinal caeca ; ////. M, dilator muscles ; N, inner nerve-o-ano-lion, 

 with circular commissure ; iY', outer nerve ; or, chitiuons lining of oral cavity ' 

 RM,Pi.d.M, retractor muscles. (After Dohrn.) 



which succeeds the masticatory apparatus is likewise provided 

 with extrinsic muscles. 



The oesophagus is followed by a 

 long gastric cavity, which sends forth 

 caecal diverticula into the chelo- 

 phores (when these are present), 

 and four immensely long ones into 

 the ambulatory legs. The caeca are 

 attached to the walls of the limb 

 cavities, especially at their extremities 

 in the tarsi, by suspensory threads 

 of connective tissue, and the whole 

 gut, central and diverticular, is further 

 supported by a horizontal septal mem- 

 brane, running through body and legs, 

 which separates the dorsal blood-vessel 

 and sinus from the gut, the nervous 

 system and the ventral sinus, giving support also to the reproduc- 

 tive glands. A short and simple rectum follows the gastric cavity. 



In Phoxichilus, which lacks the three anterior appendages in 

 the female and the two anterior in the male, two pairs of caeca run 

 from the gut into the cavity of the proboscis (Fig. 278, B, coec.)} 



Fig. 279. — Transverse section 

 through the basal joint of the 

 third leg in Phoxichilus charyb- 

 daeits, 9 . Cut, Cuticle ; Hyp, 

 hypodermis ; Int, intestinal cae- 

 cum ; N, nerve-cord ; Ov, ovary ; 

 Se}^, septum. (After Dohrn.) 



Dohni, t. cit. p. 55. 



