| Comparison with 1861 | 
  | 
and 
 becoming | becoming 1859 1860 1861 1866 |  | became 1869 1872 |  
  
a climber.  The naked skin on the head of a vulture is generally looked at 
as a direct adaptation for wallowing in putridity; and so it may be, or it may possibly be due to the direct action of putrid matter; but we should be very cautious in drawing any such inference, when we see that the skin on the head of the clean-feeding male 
 turkey | turkey 1859 1860 1861 1866 |  | Turkey 1869 1872 |  
  
is likewise naked.  The sutures in the skulls of young mammals have been advanced as a beautiful adaptation for aiding parturition, and no doubt they facilitate, or may be indispensable for this act; but as sutures occur in the skulls of young birds and reptiles, which have only to escape from a broken egg, we may infer that this structure has arisen from the laws of growth, and has been taken advantage of in the parturition of the higher animals.  | 
 | 
 We are profoundly ignorant of the 
 causes | causes 1859 1860 1861 1866 |  | cause 1869 1872 |  
  
 producing slight and unimportant variations; | producing slight and unimportant variations; 1859 1860 1861 1866 |  
| of each slight variation or individual difference; 1869 1872 |  
  
and we are immedi- ately 
made conscious of this by reflecting on the differences in 
the breeds of our domesticated animals in different 
 countries,— | countries,— 1859 1860 1861 1872 |  | countries,—more 1866 1869 |  
  
 more | more 1859 1860 1861 1872 |  more 1866 1869 |  
  
especially in the less civilized 
countries where there has been but little 
 artificial | artificial 1859 1860 1861 1866 |  | methodical 1869 1872 |  
  
selection. ↑| 1 blocks not present in  1859 1860 1861 1866 1869; present in  1872 |  |  With cattle susceptibility to the attacks of flies is correlated with colour, as is the liability to be poisoned by certain plants; so that even colour would be thus subjected to the action of natural selection. 
 |  
   
Careful  
observers 
are 
 | 
 
  
  
and 
 became | became 1869 1872 |  | becoming 1859 1860 1861 1866 |  
  
a climber.  The naked skin on the head of a vulture is generally 
 considered | considered 1861 1866 1869 1872 |  | looked at 1859 1860 |  
  
as a direct adaptation for wallowing in putridity; and so it may be, or it may possibly be due to the direct action of putrid matter; but we should be very cautious in drawing any such inference, when we see that the skin on the head of the clean-feeding male 
 Turkey | Turkey 1869 1872 |  | turkey 1859 1860 1861 1866 |  
  
is likewise naked.  The sutures in the skulls of young mammals have been advanced as a beautiful adaptation for aiding parturition, and no doubt they facilitate, or may be indispensable for this act; but as sutures occur in the skulls of young birds and reptiles, which have only to escape from a broken egg, we may infer that this structure has arisen from the laws of growth, and has been taken advantage of in the parturition of the higher animals.  | 
 | 
 We are profoundly ignorant of the 
 cause | cause 1869 1872 |  | causes 1859 1860 1861 1866 |  
  
 of each slight variation or individual difference; | of each slight variation or individual difference; 1869 1872 |  
| producing slight and unimportant variations; 1859 1860 1861 1866 |  
  
and we are 
 immediately | immediately 1861 1866 1869 1872 |  | immedi- ately 1859 1860 |  
  
made conscious of this by reflecting on the differences 
 in | in 1859 1860 1861 1866 1869 |  | between 1872 |  
  
the breeds of our domesticated animals in different 
 countries,—more | countries,—more 1866 1869 |  | countries,— 1859 1860 1861 1872 |  
  
 ..| ..... 1866 1869 |  | more 1859 1860 1861 1872 |  
  
especially in the less 
 civilised | civilised 1860 1861 1866 1869 1872 |  | civilized 1859 |  
  
countries where there has been but little 
 methodical | methodical 1869 1872 |  | artificial 1859 1860 1861 1866 |  
  
selection. ↑| 1 blocks not present in  1859 1860 1861 1866 1869; present in  1872 |  |  With cattle susceptibility to the attacks of flies is correlated with colour, as is the liability to be poisoned by certain plants; so that even colour would be thus subjected to the action of natural selection. 
 |  
    Other | Other 1861 1866 1869 |  | Careful 1859 1860 |  | Some 1872 |  
  
 observers | observers 1859 1860 1861 1866 1869 |  | observes 1872 |  
  
are 
 |