KONGL. SV. VET. AKADEMIENS HANDL. BAND. 19. N:0 7. 49 



apparently very thick lobes, separated by deep grooves, and in some cases forming 

 in the iniddle a funnel-shaped depression. 



The structure thus described, the centi^al protuberance, provided with flexible 

 lobes resembling lips, sometimes found closed, sometimes open and expanded, in a certain 

 degree calls to mind the sucking mechanism seen in Starfishes and Archa3onomous 

 Echinoids, as also in many other Echinoderms. If an Asterias rubens is brought to 

 fästen some of its pedicels on a covering-glass, and this is placed under the micro- 

 scope after the pedicels have been cut off, their tapering tops, desti- 

 tute of any calcareous support, are found to be flattened against 

 the glass, thus forming temporary disks, and their central parts are 

 seen to be drawn in conically into the tube, by the action of some 

 of its longitudinal muscles. If covering-glasses are strewn about in 

 a vessel where specimens of Toxopneustes droebachensis are kept ^ 

 alive, these readily take to lifting some of them, and keeping them (&- 

 hanging on their backs, perhaps mistaking them for fragments of 

 dead shells, like those they are said to make use of in disguising. sucking pedicei of Astedas 

 Preparations for the microscope are thus obtained of the disk in 

 adhesion, the pedicels of this species keeping their hold more persistently after am- 

 putation than do those of the Starfish. If the glass is detached by pulling, some disks 

 will let go their hold, each leaving behind a circular mark, a thin film made up of 

 fragments of its cuticula, spread all around a clear spöt in the centre, where there had 

 been no adhesion. But other pedicels will part, and their disks, left adhering to the 

 glass, Pl. XI, fig. 112 — 115, present within the broad circular and regularly waved 

 margin, a flat surface, jig. 113, in whose centre an angular depression is seen to give 

 off radiating, graduallj^ less defined plicatures. Beneath this depression bundles of 

 delicate muscular fibres come in sight converging from below, fig. 112, 114, 115, by 

 the action of which the central part is drawn in. It will appear that suction is brought 

 about in consequence of the capacity of this depression being thus increased. 



Experiments on living Spatangi are necessary, before it may be safe to conclude 

 from a certain resemblance in structure to a similarity of function, but meanwhile it 

 seems at least allowable to look upon the subanal pedicels, in the genera enumerated 

 above, as a combination of a marginal, tactual, with a central, sucking apparatus, and 

 the whole as a union of a feeler and an instrument of prehension. 



For locomotive purposes most of the Spatangidse, being normally burrowers, 

 chiefly use the strong oar-like spines of the sternum, and are never seen to climb the 

 walls of glass-vessels, as do the true Echinids by means of their powerful pedicels. 

 In close accordance with the amount of muscular exertion thus displayed by the last 

 named, stånds the superior solidity of the calcareous lamels and spicules that underlie 

 the adhesive sui'face of their disk. These have been described by various authoi's. 

 In Toxopneustes droebachensis, Pl. XI, fig. 112, four reticular laminsB, concentric and 

 adjacent to one another, and, if I am not mistaken, united by short muscles, inwardly 

 inclose a circular open space, and outwardly send out strong points, at regular inter- 



K. Sv. Vet. Akad. Handl. B. 19. N:o 7. 7 



