Vice-Presidenfs Address. 291 



There is one other line of thought to which I should like 

 to direct attention, and that is the correspondence which 

 exists between the senses and the environment. Animals, as 

 you are all aware, keep up their connection with the external 

 world by means of five senses, which are not inappropriately 

 designated the five gateways of knowledge. The media 

 through which these senses operate are more or less elabor- 

 ately constructed organs — the degree of elaboration being 

 generally in proportion to the position of the species in the 

 scale of development — ranging from the merest grouping of 

 a few nerve-cells up to the complex mechanism of the brain 

 and nervous system of the higher vertebrates. Now, what I 

 wish to point out here more particularly is the fact that 

 these different senses have extremely well-defined counter- 

 parts in the external world, in the form of light, atmospheric 

 undulations, and certain physical and chemical properties of 

 matter, so that every sense has its special excitant to which 

 it responds. 



Among the Protozoa there is great irregularity in the 

 degree of development of the senses, some having no localised 

 organs, and others only rudimentary ones. The majority of 

 the molluscs are endowed with the sense of smell, and some 

 landshells are guided to their food by taste as well. The 

 cephalopods and gastropods are furnished with visual organs, 

 while most of the bivalves are without them. 



The natural phenomena, to which the senses are thus so 

 remarkably correlated, may be regarded as constant quan- 

 tities in nature, and hence they produce cumulative effects 

 on living organisms susceptible to improvement or advance 

 in life. Altogether, they present an ideal field for the action 

 of natural selection as defined by Mr Darwin. The same 

 arguments apply to many of the mechanical contrivances by 

 means of which animals have accommodated themselves to 

 their physical surroundings. Locomotion by land, air, or 

 water was effected in each case by appropriate appliances, 

 so that the teleological argument for design in the organic 

 world resolves itself into the slow processes of harmonising 

 means with ends, by the adjustment of small increments of 

 variation extending over long periods of time. 



