146 ANTHOZOA ASTEROIDA. 



nence and width. Attached to them, and indeed forming a 

 part of them, there are an equal number of twisted somewhat 

 glandular filaments, which, originating round a small aperture 

 in the base of the stomach, appear to be suspended in the ca- 

 vity, gradually losing themselves in its depth. By most 

 authors these have been mistaken for ovaries ;* but though 

 this assignation of function to them is easily proved to be er- 

 roneous, their true office remains conjectural. Milne-Edwards 

 says they have great analogy with the biliary vessels of in- 

 sects ; f and some more recent anatomical naturalists maintain 

 that they are analogous to the testes in the Actinia?. :j: 



As already remarked, the protrusile portion of the polype is 

 very delicate, the internal viscera being as it were enclosed in 

 a serous bladder so transparent as to permit a view of their 

 disposition. This envelope is itself, however, composed of two 

 very thin membranes in intimate union : at the base of the 

 body the outer of these assumes a considerable thickness, and, 

 in coalescing w^ith that of the adjacent polypes, constitutes the 

 common cortical portion into which each animalcule retreats 

 at will by a process of invagination, which we have had occa- 

 sion already to compare to that by which a snail shortens its 

 horns. (Plate xxxiv. Fig. 2.) In the greater number of the 

 Asteroida this common portion secretes carbonate of lime, 

 which is deposited in the meshes of its tissue either in granules 

 or in crystalline spicula, and imparts more or less of consis- 

 tency to the whole. The inner tunic on the contrary con- 

 tinues unaltered, and, prolonged within the polypiferous mass, 

 it lines the cell, the abdominal cavity, and the longitudinal 

 canals which permeate the mass, as well as the very fine tubu- 

 lar net-work with which the spaces between these canals is 

 occupied (Fig. 5) ; for Milne-Edwards has shewn that there 



• Cuvier, Reg. Anim. iii. p. 309, 310, 319. Lamarck gives us Savigny's opinion 

 in the following passage : — ''Les huit intestins d'un Polype semblent de deux sortes, 

 car ils ne se ressemblent pas tous par la forme, ni vraisemblalilemcnt par les fonctions. 

 Deux d'cntre eux descendent distinctement jusque au fond du corps du Polype, et 

 n'arrivent a aucun ovaire. Les six autres, plus varies dans leur forme, selon les 

 genres, paraissent s'arreter a six grappes de gemraules oviformes qui imitent six 

 ovaires." — Anim. s. Vert. ii. p. 405-7, 417. 



t Ann. des So. Nat. iv. p. 331. 



X Owen's Lectures, p. 88. 



