Chap. VII.] THEORY OF NATURAL SELECTION. 297 



exist, the young one must infallibly be choked by the 

 intrusion of the rnilk into the windpipe. But there is 

 a 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 selec- 

 tion 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 divi- 

 sions 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 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 



