1876.] and Development o/Antedon rosaceus. 223 



the subtentacular canal, completely separating the one from the other 

 (figs. 6, 8); and it was this correspondence of position which first 

 suggested to me the real nature of Miiller's " nerve." On tracing the 

 testis or ovary to the base of the pinnule, I clearly made it out to have 

 the same relation to the lateral branch of the generative racliis of the 

 arm (h, fig. 9) as the currants forming a bunch have to the stalk that 

 bears them ; and if I am correct in deriving the generative rachis from 

 the " axial prolongations," it may be considered originally to spring from 

 the Crinoid Axis itself. 



Towards the extremities of the pinnules, especially in those that con- 

 tain no generative organs, the horizontal partition between the coeliac 

 and subtentacular canals thins away, and at last becomes obsolete ; so that 

 at the periphery of this canal-system there seems to be as free a com- 

 munication between the two sets of canals as there is between the arteries 

 and veins of the higher animals through the capillary plexus. And, for 

 reasons to be presently given, I feel strongly inclined to believe that a regu- 

 lar circulation is carried on through them, the nutritive fluid being trans- 

 mitted through one set of canals from centre to periphery, then passing 

 into the other, and being conveyed by it back from periphery to centre. 



Physiology. 



Ingestion of Food. — That the food of Antedon consists, not of the large 

 bodies grasped and swallowed by ordinary Starfish, but of minute and 

 even microscopic organisms, and that the so-called " tentacles " are 

 entirely destitute of prehensile power, was long since affirmed by 

 Dujardin on the basis of observation of the habits of the living animal 

 and of microscopic examination of the matters ejected from the vent. 

 These statements are entirely borne out by my own careful observation 

 of the actions of the brachial and tentacular apparatus, alike in the Penta- 

 crinoid and in the adult condition, and by the microscopic examination I 

 have repeatedly made of the contents of the alimentary canal. These 

 consist of minute Entomostraca, Diatoms, spores of Algae, &c, but espe- 

 cially, in my Lamlash specimens, of Peridinium tripos (Ehr.), which was 

 usually very abundant in that locality. A powerful indraught current 

 towards the mouth is maintained by the action of the large cilia that 

 fringe the villous folds of the alimentary canal ; but this does not extend 

 to any considerable distance ; and it is clear that minute particles are 

 transmitted from the peripheral extremities of the arms and pinnules, 

 along the brachial furrows and the radial furrows of the disk, to the 

 neighbourhood of the mouth, where they come within the reach of the 

 oral indraught. This I have repeatedly seen when I have had young 

 Pentacrinoids alive under the microscope ; and although I have been 

 prevented, by the peculiarity of their position, from detecting the cilia 

 to which the transmission is attributable, I can scarcely doubt that they 

 belong to the epithelial floor of the furrows. And when I have detached 



vol. xxty. E 



