274 THE WORLD OF LIFE 



as outside or inside, as skin or as stomach, as limbs or as 

 lips, so may every part of it receive a slightly different sensa- 

 tion from a touch outside or a touch inside, from an air- 

 vibration or from an ether-vibration, from those emanations 

 which effect us as noxious odours or disgusting tastes. But 

 if this view is a sound one, as I think it will be admitted 

 that it is, how absurd is it to ask, " How did the eye or the 

 ear begin ? " They began in the potentiality of that marvel- 

 lous substance, protoplasm, and they were rendered possible 

 when that substance was endowed with the mysterious or- 

 ganising power we term life. First the cell was produced; 

 and, from the continued subdivision of the cell at each sub- 

 division taking a slightly different form and function, numer- 

 ous one-celled animals were formed; and a little later the 

 union of many cells of diverse forms and functions led to the 

 endless multicellular creatures, constituting the entire world of 

 life. 



Thus every substance and every organ came into existence 

 when required by the organism imder the law of perpetual 

 variation and survival of the fittest, only limited by the 

 potentialities of living protoplasm. And if the higher sense- 

 organs were so produced, how much easier was the production 

 of such superficial appendages as horns and tusks, scales and 

 feathers, as they were required. Horns, for instance, are 

 either dermal or osseous outgrowths or a combination of both. 

 In the very earliest known vertebrates, the fishes of the 

 Silurian formation, we find the skin more or less covered with 

 tubercles, or plates, or spines. Here we have the rudiments 

 of all those dermal or osseous outgrowths which continue in 

 endless modifications through the countless ages that have 

 elapsed down to our own times. They appear and disappear, 

 as they are useful or useless, on various parts of the body, 

 as that body changes in form and in structure, and modifi- 

 cations of its external covering are needed. Hence the in- 

 finite variety in nature — a variety which, were it not so 

 familiar, would be beyond the wildest flights of imagination 



