40 REPORT ON THE PENNATULIDA. 



the polype : its walls are thrown into transverse folds, which, when 

 the polype is retracted, are approximated like the folds of a concertina 

 so as to reduce the stomach to less than half its normal length. 



The walls of the stomach agree in structure with those of Funiculina, 

 consisting of a thin glandular linmg membrane or ectoderm which is 

 distinctly ciliated, a thin connective-tissue mesodermal layer, and a 

 moderately thick outer or endodermal layer, containing numerous 

 spherical highly refractive granules similar to those described in 

 Finunulina. 



e. Till' }fi'>:i'ntrrii'.'< (Figs. 4 and o o), eight in number, connect the 

 stomach with the body wall, and extend below the stomach the whole 

 length of the polype, as far down as 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 filameuts s ; and a 

 set of six which bear the short mesenterial tilaments 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 stoinach the eight mesenteries are arranged at nearly 

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

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

 towai'd 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 neighbours on either side. 



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

 terial filaments, the six mesenteries become more irregularly arranged ; 

 they now form (vide Fig. 4 o and the three lower sections in Fig. o o) 

 very small longitudinal ridges, only projecting a verj' 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 shortly below the lower ends 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 Funicidimi. The retractor muscles 

 of the polype (Figs. 4 and 5 p) ariBe 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 like the 

 i-etractors into the stomach wall. 



