178 MISCELLANEOUS OBJECTIONS TO THE [CHAP. VIL 



special provision. The larynx is so elongated that it rises up into 

 the posterior end of the nasal passage, and is thus enabled to 

 give free entrance to the air for the lungs, while the milk passes 

 harmlessly on each side of this elongated larynx, and so safely 

 attains the gullet behind it." Mr. Mivart then asks how did 

 natural selection remove in the adult kangaroo (and in most 

 other mammals, on the assumption that they are descended from 

 a marsupial form), " this at least perfectly innocent and harmless 

 structure ? " It may 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 swallowing 

 solid food. 



We will now turn for a short space to the lower divisions of 

 the animal kingdom. The Echinodennata (star-fishes, sea-urchins, 

 tfcc.) are furnished with remarkable organs, called pedicellariae, 

 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 par- 

 ticles of excrement 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 would be the utility of the 

 first rudimentary beginnings of such structures, and how could 

 such incipient buddings have ever preserved the life of a single 

 Echinus 1 " He adds, " not even the sudden development of the 

 snapping action could have been beneficial without the freely 

 moveable stalk, nor could the latter have been efficient without 

 the snapping jaws, yet no minute merely indefinite 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 pedi- 



