EECOGXITIOX-MAEKS 179 



^^ Consequently it appears certain that most of these species were 

 developed singly, each in its own island. If this he the case, 

 the colours which now distinguish tlic dilferent species cannot be 

 recognition-marks, because there is no other species in each island 

 with which they could be confounded." 



Shortly afterwards the late Dr. St. George Mivart made 

 the same objection as regards the very numerous species of 

 beautifully coloured, lories Avhich are found in all the islands 

 around Xew Guinea and in the Western Pacific. He urijed 

 that the various peculiarities of colour cannot be useful as 

 recognition-marks, because the colour and markings of each 

 of the 2,'enera of these birds is so very distinct from that of 

 all other birds inhabiting the same island, and there is usually 

 only one species in each island. This argument, looked at 

 superficially, seems very strong, but it is not difficult to show^ 

 that it is a complete fallacy, if we follow out in detail what 

 must have occurred in each case. 



It is clear, admitting evolution (as both these writers did 

 admit it), that each of the species of pigeon or lory noW' 

 peculiar to an island must have originated from some parent 

 species in the same or some other island; and there are only 

 tw^o possible suppositions — either the species originated in is- 

 land A by modification of the present form, and then migrated 

 to island B, afterwards becoming extinct in A ; or it migrated 

 from A to B and became modified into its present form in 

 B. The latter case is by far the more probable, and as it is 

 clearly that which the critics contemplated, let us see exactly 

 what must have happened. 



We know as a fact that, when any species reaches an is- 

 land or other new habitat for the first time, if the conditions 

 are favourable, it increases with marvellous rapidity, till the 

 island is fully stocked, and the supply of food at some time 

 of the year begins to fail, or till some enemy — a rapacious 

 bird, for instance — finds out the rich banquet, and is soon 

 followed by others. The rabbit in Xew Zealand and Porto 

 Santo, the sparrow in the United States, and many others, 



