132 



The tentacles, or the pores of the retracted tentacles, form a 

 circlet half-way between the epitheca and the stomodoeum, 

 and the peristome is irregularly contracted into ridges 

 between the attachments of the mesenteries. The stomo- 

 doeum may be either extremely reduced or enormously 

 enlarged, the former if the polyp has been slowly killed in 

 spirit or chromic acid, the latter if more rapidly fixed in 

 formalin. To a certain extent the appearance and t^ize of 

 the stomodoeum depends on the state of retraction of the 

 tentacles, being much larger when the latter are but partially 

 invaginated. 



Fig. I. Partly diagrammatical transverse section through a single completely 

 rttracted specimen of 7''. rubrum indifferent planes: — A. Through the top of the 

 epitheca a little below its edge: B. Through the stomodoeum, cuttiug ihe basal 

 contracted ends of some of ihe tentacles: C. Through the top tf thi maafes of 

 g< nerative organs : D. Through the bottom part ot' the generative organs. 



The numerals refer to the cycles of the septa, t. Tentacles, -st. Stomodoeum. 

 ^.((?. Ptristome wall w./. Mesenterial filaments. // Testicular masses. 



The sections were sb'ghtly simplified from camera iucida drawings. In addi- 

 tion to the general anatomy they show the decrease in size ai d disappearance of the 

 mesenteries and septa lower down in the corallite. One of the mesenteries of a 

 pair bounding a septum of cycle 4 reaches the stomod' eum (see B) and is so repre- 

 sented, although it is very unusual for such an one to do so. 



Septa and Mesenteries.— When decalcified, the polyp is 

 divided up into as many chief segments as there are larger 

 septa. These are joined over the open mouth of the calicle by 



