214 MANUAL OF ZOOLOGY. 



the animal has the power of creeping about by means of its 

 pinnated arms. Though capable of creeping, the animal more 

 usually has recourse to swimming, the five left arms working 

 as paddles simultaneously, and alternating in their action with 

 the five right arms. The arms of Comatula rosacea exhibit-on their 

 ventral surface a deep "brachial groove," the elevated margins 

 of which are cut out into minute crescentic respiratory leaves, 

 at the base of each of which is a group of three tentacles, con- 

 nected with a cavity in the interior of the respiratory leaf, and 

 communicating by a common trunk with the radiating ambu- 

 lacral vessel. The floor of the brachial grooves is ciliated, and 

 underneath each runs a radiating ambulacral vessel, together 

 with a blood - vascular trunk, and a peculiar fibrillar "sub- 

 epithelial band," which is supposed to be of a nervous nature. 

 In some Comatulids (certain Actinometrce) there is the curious 

 feature that some of the arms in some individuals may want 

 the ventral grooves, tentacles, and nerves, while in other in- 

 dividuals all the arms possess these structures. The dorsal 

 surface of the calyx, again, carries a tuft of jointed filaments or 

 cirri, by which the animal is enabled to moor itself temporarily 

 to foreign objects. 



The animal feeds upon very minute organisms which are 

 conveyed to the mouth by the action of the cilia lining the 

 brachial grooves. The mouth in C. rosacea is sub-central, but 

 in some Comatulids (Actinometrd) it is quite excentric ; while 

 the anus is usually supported on a tubular projection and 

 situated on one side. According to the researches of Dr 

 W. B. Carpenter, the nervous system of Comatula consists of a 

 fibrillar sheath surrounding a central quinquelocular vascular 

 organ, and giving off a series of radial branches which differ 

 from the radial nerve-cords of the other Echinoderms in not 

 running along the ventral surface of the arms, but in occupying 

 a median canal in the centre of each arm. While the principal 

 nerve-cords have this position, and have a motor function, it 

 has also been shown that there exists, as before remarked, a 

 fibrillar band below the epithelial lining of the ventral furrow 

 of each arm, and these bands are supposed to be of the nature 

 of sensitive nerves. They spring from a circular band, which is 

 placed round the gullet, above the ambulacral and blood-vas- 

 cular rings. It has also been shown by modern researches, that 

 there exists in Comatula a complicated blood-vascular system. 



As regards the vascular system of the Crinoids generally, there is found 

 in Comatula, occupying the dorso-ventral axis of the body, a largish lobated 

 structure homologous with the heart of the Asteroids, and, like it, consist- 

 ing of numerous closely-packed vessels. Dorsally, these resolve them- 



