150 REPORT ON THE PENNATULIDA. 



e. The Mesenteries, Figs. 4 and 5 o, eight iu number, connect the 

 stoniach to the body wall, and extend below the stomach the whole 

 length of the polype, right down to the rachis. They may be divided 

 into a set of two, situated on the upper surface of the leaves, and 

 bearing below the stomach the long mesenterial filaments s ; and a 

 set of six which bear the short mesenterial filaments r, and of which 

 two are attached to the under surface of the leaf, two to the dorsal wall 

 of the polype, and two to the ventral wall. 



Around the stomach the eight mesenteries are arranged at nearly 

 equal intervals, as shown iu the second section of Fig. 5 ; but even 

 here it will be noticed that the mesenteries are rather closer together 

 toward the right-hand side of the figure, corresponding to the lower 

 surface of the leaf, than they are on the left-hand side of the figure, or 

 upper surface of the leaf. 



Below the stomach, this asymmetry becomes still more marked, 

 the set of six mesenteries becoming crowded together towards the 

 under side of the leaf, while the two upper mesenteries, bearing the 

 long mesenterial filaments s, move slightly away from one another, and 

 become situated as shown in the lower section of Fig. 5, close to the 

 partitions dividing the polype from its laeighbours on either side. 



Still nearer the rachis, i.e., below the lower end of the short mesen- 

 terial filaments, the six mesenteries become more irregularly arranged ; 

 they now form {ride Fig. 4 o and the three lower sections in Fig. 5 o) 

 very small longitudinal ridges, only projecting a very short way into 

 the cavity of the polype ; as a rule, three of the six are situated on the 

 under surface of the leaf, owing to one of the lateral ones shifting its 

 attachment from the side to the under surface. This arrangement, 

 which is acquired shortlj' below the lower end of the short mesenterial 

 filaments (Fig. 4 r) persists down to the bottom of the polype cavity. 



The structure of the mesenteries and the arrangement of their 

 muscular system is the same as in Funiculina. The retractor muscles 

 of the polype — Figs. 4 and 5 p — arise from the body wall and run up in 

 the mesenteries to be inserted into the mesodermal layer of the 

 stomach ; while the protractor muscles — Fig. 4 q — which are much 

 feebler, arise from the upper part of the sides of the body, and running 

 downwards and inwards in the mesenteries, are inserted, Uke the 

 retractors, into the stomach wall. 



As shown m the second section of Fig. 5, the protractor muscles are 

 situated on one face only of the mesenteries, and a comparison of this 

 figure with Fig. 13 of Plate II. will show that the actual arrangement 

 is the same as iu Funiculina. The two upper mesenteries, which bear 

 below the stomach the long mesenterial filaments, and are situated on 

 the left hand side of both the figures referred to, have the retractor 

 muscles on the sides facing away from one another ; the two opposite 

 mesenteries, those on the lower surface of the leaf and the right hand 

 side of the figures, have the retractor muscles on the sides facing one 

 another, while the intermediate or dorsal and ventral mesenteries bear 

 the muscles on their right hand sides in the figures. 



