The British Star-Fishes. 255 



despair I grasped at the largest, and brought up the extremity 

 of an arm with its terminating eye, the spinous eyelid of which 

 opened and closed with something exceedingly like a wink of 

 derision." It may be added, that even had the Professor 

 succeeded in " introducing Luidia to the purer element/' it is 

 very probable that his expectation of procuring a perfect 

 cabinet specimen would not have been realized, for fresh 

 water, though it mostly seems to paralyze and kill star-fishes 

 instantaneously, thus preventing their breaking up, does not 

 act so favourably on Luidia. The creature may be put at once 

 into cold fresh water, and will lie there for some time breaking 

 itself to pieces. The only way in which (so far as I know) this 

 can be avoided is to press the disk of the animal forcibly down 

 with the hand until it is dead. In this way its destructive con- 

 tractions may be prevented. 



The cirrhigrade star-fishes are furnished with certain curious 

 appendages, the use of which is at present very imperfectly 

 understood. These are the " ■pediceTiarice. : "' and " 'madrepori- 

 form tubercle." The latter is a rounded, cushion-like eminence 

 of considerable size, situated on the disk, mostly very much out 

 of the centre. It is irregularly fissured in a radiate manner, 

 and is not at all unlike the animal from which it derives its 

 name. It is found to communicate beneath with a short canal, 

 which is connected with the vascular system of the star-fish. 

 Yarious conjectures have been made as to the use of the madre- 

 poriform tubercle. It has been supposed to act either as a 

 secreting organ for the calcareous elements of the animal, or to 

 filter out the impurities of the circulating fluid. Professor 

 Porbes looks upon it as being merely the analogue of the stalk 

 which exists in the young condition of the crinoid star-fishes : 

 if this be really the case it must be considered as a rudimentary 

 organ without any specific function. The pedicellarice are pincer- 

 like organs which, are irregularly scattered over the surface of 

 the animal, and which have distinct characters in the different 

 species. They were for long supposed to be parasitic creatures, 

 but are now generally admitted to be true epidermic appen- 

 dages. They are in constant active motion during the life of 

 the star-fish, and grasp firmly anything which is brought 

 between their blades.* Their nearest analogues are the birds' - 

 head processes which occur in certain zoophytes, and which 

 Mr. Grosse believes to serve the purpose of seizing organic mat- 

 ters, and by holding them in their grasp to provide food for 

 the animal in an indirect manner; for the decomposition of 

 the captured morsel in time attracts round it clouds of infu- 

 soria?, which are swept into the stomach of the polyp by its 

 vigorous ciliary action. It is needless to say, that although 

 * One of the pedicellariee of Uraster ruhens is shown at f, in the woodcut. 



