Chap. VII.] THEORY OP NATURAL SELECTION. 297 



that the habit was at first acquired by practice at a 

 more advanced age, and afterwards transmitted to the 

 ofEspring at an earlier age. But the young kangaroo is 

 said not to suck, only to cling to the nipple of its 

 mother, who has the power of injecting milk into the 

 mouth of her helpless, half-formed offspring. On this 

 head, Mr. Mivart remarks: "Did no special provision 

 exist, the young one must infallibly be choked by the in- 

 trusion of the milk 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 an- 

 swer 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 tridacytle forceps — that is, of one formed 

 of three serrated arms, neatly fitting together and 

 placed on the summit of a flexible stem, moved by mus- 

 cles. These forceps can seize firmly hold of any object; 



