Page - 246 - in The Origin of Species

246 ORIGIN OF SPECIES be suggested in answer that the voice, which is certainly of high importance to many animals, could hardly have been used with full force as long as the larynx entered the nasal passage ; and Professor Flower has suggested to me that this structure would have greatly interfered with an animal swal- lowing solid food. We will now turn for a short space to the lower divisions of the animal kingdom. The Echinodermata (star-fishes, sea-urchins, &c.) are furnished with remarkable organs, called pedicellarise, which consist, when well developed, of a tridactyle forceps—that is, of one formed of three serrated arms, neatly fitting together and placed on the summit of a flexible stem, moved by muscles. These forceps can seize firmly hold of any object; and Alexander Agassiz has seen an Echinus or sea-urchin rapidly passing particles of excre- ment from forceps to forceps down certain lines of its body, in order that its shell should not be fouled. But there is no doubt that besides removing dirt of all kinds, they subserve other functions; and one of these apparently is defence. With respect to these organs, Mr. Mivart, as on so many previous occasions, asks : "What v/culd be the utility of the iirst rtiSmentary beginnings of such structures, and how could such incipient buddings have ever preserved the life of a single Echinus ?" He adds, "not even the sudden develop- ment of the snapping action could have been beneficial with- out the freely moveable stalk, nor could the latter have been efficient without the snapping jaws, yet no minute merely in- definite variations could simultaneously evolve these complex co-ordinations of structure ; to deny this seems to do no less than to affirm a startling paradox." Paradoxical as this may appear to Mr. Mivart, tridactyle forcepses, immovably fixed at the base, but capable of a snapping action, certainly exist on some star-fishes; and this is intelligible if they serve, at least in part, as a means of defence. Mr. Agassiz, to whose great kindness I am indebted for much information on the subject, informs me that there are other star-fishes, in which one of the three arms of the forceps is reduced to a support for the other two; and again, other genera in which the third arm is completely lost. In Echinoneus, the shell is described by M. Perrier as bearing two kinds of pedicellarise, one re-