io8 Evolution of the Eye. 



table contrivances and marvellous adjustments, 

 formed ? The lowest animals, and probably our 

 remotest ancestors, had no eyes, or any other sense 

 than touch. We can imagine that the first stage in 

 the development was a slightly heightened sense 

 of feeling at some spot in the organism. If it 

 gave the animal an advantage over others, either 

 in procuring food or in defending himself, or in 

 any other way, it would enable him to vanquish 

 his rivals and perpetuate his advantageous modi 

 fications ; and if the variability in that direction 

 continued, animals possessing it would in surviv 

 ing accumulate it, until, after the lapse of mill 

 ions of years, the sensitivity might have solidi 

 fied into something like the pigment-cells that 

 constitute the lowest organs of vision now in ex 

 istence. It is at this point Darwin takes up the 

 problem. The apparatus of an optic nerve, 

 coated with pigment and invested by transparent 

 membrane, is only one step onward ; and when 

 we reflect on the wide, diversified, and graduated 

 range of ocular structure in the lower animals, 

 &quot; the difficulty,&quot; according to Darwin, &quot; ceases 

 to be very great in believing &quot; that natural selec 

 tion may have converted this simple apparatus 

 into an eye as perfect as man s or the eagle s, with 

 all its wonderful arrangements for admitting 





