60 



ANTHOZOA. 



cate freely with the great abdominal cavity (e), and the vertical parti- 

 tions whereby they are separated become continuous with the longi- 

 tudinal folds (f ) visible in its interior. The longitudinal plicae are 

 apparently of the same structure as the vertical septa of which they are 



Fig. 26. 



Anatomy of Aleyonidium elegans (after Milne-Edwards). 1. A polyp opened longitudinally to 

 show its internal organization: a, the tentacula; 6, mouth; c, alimentary canal; d, inferior open- 

 ing of ditto; e, upper portion of the abdominal cavity;,/, longitudinal septa passing between the 

 parietes of the body and the walls of the digestive cavity; f, continuation of the same into the 

 abdominal cavity; g, canals formed between the septa, which are continuous with the interior of 

 the tentacula; g', one of the tentacles opened, showing the holes by which its cavity communicates 

 with those of the marginal pinnules ; h, minute spicula situated at the base of the tentacles ; 

 k, filiform appendages to the alimentary tube. 2. Transverse section, showing the manner in 

 which the longitudinal plicae are connected with the alimentary tube. 3. Section through the 

 basilar portion of the polypary. 



the continuations, only they are narrower, and their inner margin being 

 free, they hang loosely in the abdomen of the polyp. On closer inspec- 

 tion they seem to be made up of two extremely thin membranous 

 layers folded upon each other and continuous with the internal tunic 

 that lines the parietes of the body. At the point of continuity the two 

 laminae become slightly separated, so as to leave a little canal at the base 

 of each fold; while superiorly, close to the termination of the stomach, 

 there is a remarkable filiform and very flexuous organ (fig. 26, 1, &), 

 apparently an appendage to the alimentary cavity. 



(128.) As has been stated above, the common polypary consists of 

 two portions differing widely from each other in texture, forming the 

 trunk and the foot. By dissection it becomes immediately apparent 

 that the softer portion, named the trunk, is made up of membranous 

 tubes disposed longitudinally parallel to each other, and so closely con- 



