Miscellaneous. 69 



of t'ifjht portions, each iiearlj' of a square form and correspondinp; to 

 the base of a tentacle ; the eight parts are separated by raphes, wliich 

 are only the lines of insertion of the mesentcroid laminsD upon the 

 peristome. 



4th. Tentacular muscles. — Each partition separating the peri- 

 gastric ca\'itics gives origin above to two distinct muscles, which rise 

 to the right and left into the two tentacles bordering u])on the parti- 

 tion. Each tentacle thus receives two tentacular muscles, coming 

 from the two septa bounding the perigastric cavity to which tlie 

 tentacle corresponds. They ascend to the summit of the organ, ap- 

 proaching each other at a very acute angle. 



5th. Intertentacular muscle. — In the angle formed by two neigh- 

 bouring tentacles, we may clearly distinguish a muscular bundle 

 which marks that angle and ascends on each side upon the borders 

 of the two tentacles for nearly half their length. 



These numerous muscles are inserted everp\'here upon the funda- 

 mental substance of the animal, and in most cases are applied 

 against it. This substance limits externally the body of each polype. 

 It emits thin expansions, which serve above as a solid framework to 

 the mesentcroid lamina), bound the perigastric cavities, and are 

 connected intornally with another equally delicate lamina supporting 

 the Avails of the stomachal cavity. ExtornaUy this substance, 

 whether upon the body of the polypes or between them, is nowhere 

 covered with epithelium. It therefore remains in contact with the 

 surrounding medium (like the bony tissue of the dermal plates of 

 certain fishes). It follows from this, at least in this state of deve- 

 lopment of the Alcyonarian, that the fundamental substance does not 

 correspond to the definition recently given of the so-called conjunc- 

 tive tissiU'S, wliich have been said to be " every tissue, with the ex- 

 ception of nerves or muscles, occurring between the external epi- 

 thelial layer and the internal epithelial layer." This fundamental 

 substance, both in the walls of the body of the polype and in the 

 mass of the ccenenchyma, is everywhere identical. 



It is fibrous in some places, and excavated by cavities of several 

 kinds; and it is always in the midst of it, in places where it is perfectly 

 homogeneous, that the spicules appear and become developed. Each 

 polype is therefore in intimate relation of structure with the 

 coeuenchyma by its constituent tissues. But the identity does not 

 stop there, and "we find it even in the tissues belonging to the group 

 of products. 



Throughout their length the wide canals are lined with the same 

 vibratile epithelium, which is continued into the perigastric cavities, 

 the tentacles, and the pinnules (A. dif/itatum). It is formed of 

 spherical or sUghtly polyhedral cells of small dimensions. Those of 

 the surface bear extremely delicate vibratile cilia, which appear to 

 be but few upon each cell, and exhibit imperfectly rhythmical 

 movements. The body of the cells appears to be formed of granula- 

 tions enclosed in a hyahne substance. No nucleus is to be dis- 

 tinguished. 



On the other hand, the epithelium which clothes the surface of 



