384 



ZOOLOGY 



SECT. 



tube-feet, where it consists of two strata, and is also well developed 

 on the ampullae and Polian vesicles. 



The stone-canal is enfolded in the wall of a wider canal, the 

 axial sinus (Fig. 309, ax. s), which forms a part of the perihaemal 

 system already referred to. The axial sinus runs nearly vertically. 

 At its oral end it opens into the internal division of the oral ring 



fit/I. ccec 



. ccec 



FIG. 308. Anthenea flavescens. Upper view of a dissection of the internal organs. The 

 aboral wall of the body, with the exception of a small portion round the anus and the madre- 

 porite, has been completely removed. One of the five intestinal caeca has been removed with 

 the exception of its proximal part. All the ovaries have been removed except one pair, and 

 four of the pairs of pyloric caeca have been cut away close to their bases. 1 5, the five rays 

 with then- ambulacral ridges ; amp. ampullae ; an. anus ; int. ccec. intestinal cueca ; 1. p. cut 

 ends of the inter-radial partitions ; mad. madreporite with the madreporic canal ; ov. ovaries ; 

 pol. ves. Polian vesicles ; pyl. ceec. pyloric caeca ; retr. retractor muscles inserted into the 

 cardiac division of the stomach. 



sinus ; aborally it approaches close to, if it does not actually open 

 into, an aboral ring sinus : it also communicates aborally with the 

 stone-canal, and perhaps opens on the exterior through certain of 

 the pores in the madreporite. 



Accompanying the madreporic canal and also enfolded in the wall 

 of the axial sinus there is an organ the axial organ (Fig. 309, 

 g. stol) the relationships and function of which have given rise 



