EXTEXSIOXS OF DARWINISM 273 



for burrowing, for swimming, or for flying, and that their 

 first appearance goes back to PalaBozoic times in the paired 

 fins of early fishes, while their actual or'ujiii must have been 

 much further back, in creatures whose skeleton was not suffi- 

 ciently solidified to be preserved. 



There is, however, a more general explanation even than 

 this, and one that applies to what has always been hehl to 

 be the most difiicult of all — that of the origin of the organs 

 of sense. 



The various sensations by which w^e come into relation with 

 the external world — sight, hearing, smell, taste, and touch 

 ■ — are really all specialisations of the last and most general, 

 that of material contact. We hear by means of a certain 

 range of air-waves acting on a specially constructed vibrating 

 organ ; we smell by the contact of excessively minute particles, 

 or actual molecules, given off by certain substances ; we taste 

 by the action of soluble matter in food on the papilke of the 

 tongue; and we see by the impact of ether-vibrations on the 

 retina; and as other ether-vibrations produce sensations of 

 cold or warmth, or, when in excess, acute pain, in every part 

 of the body, the modern view, that matter and ether are funda- 

 mentally connected if not identical, seems not unreasonable. 



Xow, as all our organs of sense, however complex, are built 

 up from the protoplasm which constitutes the material of all 

 living organisms, and as all animals, however simple, exhibit 

 reactions which seem to imply that they have the rudiments 

 of most, if not all of our senses, we may conclude that just 

 in proportion as they have advanced in complexity of organi- 

 sation, so have special parts of their bodies become adapted 

 to receive, and their nervous system to respond to, tlio varinn? 

 contacts with the outer world which produce what wo terra 

 sensations. There is therefore, probably, no point in the 

 whole enormous length of the cliain of being, fnnn ourselves 

 back to the simple one-celled Amoeba, iu which the rudiments 

 of our five senses did not exist, although no separnto organs 

 may be detected. Just as its whole body sen'os alternately 



