With respect to the effects of this intercrossing, it | With respect to the effects of this intercrossing, it 1860 1861 1866 |  
| It 1869 1872 |  
  
should be 
 remembered | remembered 1860 1861 1866 |  
| borne in mind 1869 1872 |  
  
that the offspring of such crosses would 
 almost | almost 1860 1861 1866 1869 |  almost 1872 |  
  
certainly gain in vigour; so that even an occasional cross would produce more effect than might 
 at first | at first 1860 1861 1866 |  at first 1869 1872 |  
  
 be | be 1861 1866 |  | have been 1860 1869 1872 |  
  
anticipated. 
 To | To 1860 1861 1866 |  | I will 1869 1872 |  
  
give a few 
 examples: | examples: 1860 1861 1866 |  
| illustrations of the foregoing remarks: 1869 1872 |  
  
in the Galapagos Islands 
 there are 26 land-birds; of these 21 (or perhaps 23) | there are 26 land-birds; of these 21 (or perhaps 23) 1866 1869 1872 |  
| nearly every land-bird, but only two out of the eleven marine birds, 1860 |  
| there are 26 land-birds; of these, 21 (or perhaps 23) 1861 |  
  
are 
 peculiar, | peculiar, 1861 1866 1869 1872 |  | peculiar; 1860 |  
  
 whereas of the 11 | whereas of the 11 1861 1866 1869 1872 |  
| and it is obvious that 1860 |  
  
marine birds 
 only 2 are peculiar; and it is obvious that marine birds only 2 are peculiar; and it is obvious that marine birds could | only 2 are peculiar; and it is obvious that marine birds only 2 are peculiar; and it is obvious that marine birds could 1866 |  
| could 1860 |  
| only 2 are peculiar; and it is obvious that marine birds could 1861 1869 1872 |  
  
arrive at these islands 
 more easily | more easily 1860 1861 1866 |  
| much more easily and frequently 1869 1872 |  
  
than land-birds. ↑| 1 blocks not present in  1860 1861 1866 1869 1872; present in  1859 |  |  Thus in the Galapagos Islands nearly every land-bird, but only two out of the eleven marine birds, are peculiar; and it is obvious that marine birds could arrive at these islands more easily than land-birds. 
 |  
   
Bermuda, on the other hand, which lies at about the same distance from North America as the Galapagos Islands do from South America, and which has a very peculiar soil, does not possess 
 one endemic land-bird; | one endemic land-bird; 1860 1861 1866 |  
| one endemic land bird; 1859 |  
| a single endemic land-bird; 1869 1872 |  
  
and we know from Mr. J. M. 
 Jones's | Jones's 1859 1860 1861 1866 1872 |  | Joness 1869 |  
  
admirable account of Bermuda, that very many North American 
 birds | birds 1866 1869 1872 |  | birds, 1859 1860 1861 |  
  
 occasionally visit | occasionally visit 1866 |  
| during their great annual migrations, visit either periodically or occasionally 1859 1860 1861 |  
| occasionally or even frequently visit 1869 1872 |  
  
this island.  Almost every year, as I am informed by Mr. E. V. Harcourt, many European and African birds are blown to Madeira; this island is inhabited by 99 kinds, of which one alone is peculiar, though very closely related to a European form; and three or four other species are confined to this island and to the Canaries.  
So that 
 the two | the two 1866 |  | these two 1859 1860 1861 |  | the 1869 1872 |  
  
 islands | islands 1859 1860 1861 1866 1869 |  | Islands 1872 |  
  
of Bermuda and Madeira have been stocked 
 by | by 1859 1860 1861 1866 |  
| from the neighbouring continents with 1869 1872 |  
  
birds, which for long ages have 
 struggled together in their former homes, and have | struggled together in their former homes, and have 1859 1860 1861 1866 |  
| struggled together, and 1869 |  
| there struggled together, and have 1872 |  
  
become mutually 
 adapted to each other; and when settled in their new homes, each kind will have been kept by the others to its proper place and habits, and will consequently have been little liable to modification. | adapted to each other; and when settled in their new homes, each kind will have been kept by the others to its proper place and habits, and will consequently have been little liable to modification. 1866 |  
| adapted to each other; and when settled in their new homes, each kind will have been kept by the others to their proper places and habits, and will consequently have been little liable to modification. 1859 1860 1861 |  
| adapted; hence when settled in their new homes, each kind would be kept by the others to its proper place and habits, and would consequently be but little liable to modification. 1869 |  
| co-adapted. 1872 |  
   Any tendency to modification 
 will | will 1861 1866 1872 |  | will, 1860 |  | would 1869 |  
  
 also | also 1861 1866 1869 1872 |  | also, 1860 |  
  
 have been | have been 1860 1861 1866 1872 |  | be 1869 |  
  
checked by intercrossing with the unmodified 
 immigrants | immigrants 1860 1861 1866 1869 |  | immigrants, 1872 |  
  
 from | from 1860 1861 1866 1869 |  
| often arriving from 1872 |  
  
the mother-country.   Madeira | Madeira 1861 1866 1869 1872 |  | Madeira, 1859 1860 |  
  
 again | again 1861 1866 1869 1872 |  | again, 1859 1860 |  
  
is inhabited by a wonderful number of peculiar land-shells, whereas not one species of sea-shell is 
 peculiar | peculiar 1866 1869 1872 |  | confined 1859 1860 1861 |  
  
to its 
 |