CHAP. XXVIII.] SPECIAL CHANGES. 417 



place from the introduction by man of a single 

 animal into a country where it was before unknown ! 

 If a geological cause, such for instance as a diminu- 

 tion of the size of the island, attended by an altera- 

 tion in the climate and a diminution of the means 

 of subsistence, has contributed to the extinction of 

 the struthious moa in New Zealand, and of the 

 dodo in the Mauritius, it is no less sure that, since 

 New Zealand began to be inhabited by its aboriginal 

 race, the agency of man has effected a part of that 

 eternal fluctuation in the organic world, the know- 

 ledge of which has been one of the most important 

 results of modern science. The introduction of the 

 dog, the cat, and the rat, the first of which, some- 

 times called pero (Pero, Spanish}, was probably first 

 brought here by the Spaniards, must have produced 

 great changes, and undoubtedly diminished the 

 number of some other classes of animals ; they are 

 perhaps the cause that the New Zealand quail 

 (Coturnix Novae Zelandise, Quoy et Gaim.) is so 

 scarce in the northern island, and also the guana. 

 Similar changes have also been effected in the vege- 

 table kingdom by the introduction of European 

 plants and by the operations of man. The common 

 dock (Rumex crispus) already covers large districts, 

 in spite of all the efforts of the Europeans to eradi- 

 cate it : how much the destruction of the forest by 

 fire has favoured the spreading of certain species of 

 indigenous plants I have already pointed out 



The shores of the Piako in this part of its course 

 VOL. i. 2 E 



