The movements of the tube-feet may also be seen to advantage when the starfish is laid upside down in a pool, and, what is still more interesting, the manner in which the animal turns itself over. To do this it will first bend the tips of one or two of its arms so as to bring the suckers against the ground; and then, aided by the pulling action of these, it will gradually bring other suckers into a similar position till, at last, the whole body has been turned over. Some of our common starfishes have rays so short that they may be termed angles rather than arms, and these are unable to turn their inverted bodies by the gradual method just described. They generally raise their bodies on the tips of three or four of the rays, assuming somewhat the form of a three-or four-legged stool, and then, bending the remaining one or two arms over the body, they alter the position of the centre of gravity till eventually the body topples over to the desired position. Some of the common five-rayed stars have no suckers on their tube-feet, and consequently have to creep by means of the muscular contractions of their arms; and several of them are like the brittle stars in breaking up their bodies when irritated or seized. This latter peculiarity will account for the frequency with which we come across animals with one or more rays smaller than the others, the smaller rays being new ones that have been produced in the place of those lost. Again, we sometimes meet with such monstrosities as a five-rayed star with six or more rays, some smaller than others, the smaller ones representing two or more that have grown in the place of one that has been lost; or a starfish with branched or forked arm, illustrating the tendency to produce a new arm even when the original one has been only partially severed. A close observation of a starfish in water may enable us to detect a number of little transparent processes standing out between the prominences of the rough skin of the upper surface. These are little bags filled with fluid, formed of such thin walls that gases can readily pass through them, and are undoubtedly connected with the process of respiration. Also, on the upturned extremity of each arm a red spot may be seen; and this from the nature of its structure, and from its association with the nervous system, has been regarded as a rudimentary eye.