president’s address. 5 
to attain any real success as a naturalist. He further ex- 
plained that the subject chosen was of so vast and important 
a character that only a rapid survey of it could be given at 
one evening’s sitting. Dr. Thomson then proceeded to 
indicate what a nervous system is, and defined it as 
a mechanism, and an infinitely complicated one, for enabling 
a living organism to make use of and benefit by the physical 
forces of Nature in the environment of that organism. For 
example, surrounding matter, light, heat, sound, &c., can 
only be discerned and made use of by our sense organs, touch, 
sight, hearing, &c., these sense organs being specially attuned 
to respond to stimulation by these physical forces, the eye to 
the stimulation of light, the skin to the contact of surrounding 
matter, and the ear to the vibrations of sound waves, and so 
on. These sensory impressions are conveyed to the central 
nervous system, brain and spinal chord, in the higher animals, 
and they are there appreciated and sorted out, so to speak. 
It remains for the brain to determine if any action is necessary 
to be taken as the result of these stimuli ; whether there shall 
be mere reception and inaction, or whether any active move- 
ment shall result ; if the latter, “ motor ” or movement 
impulses are transmitted through a motor nerve to a muscle, 
when, of course, movement results. This, then, is the 
essential mechanism, and it is found more or less highly 
organised in all living organisms, from the almost structure- 
less Amoeba, a very lowly form of Protozoan animalcule, 
right through the animal series till man himself is reached. 
The lecturer then proceeded to detail the mechanism 
of the nervous system in typical members of the various 
phyla, or species of animals in the Invertebrates ; first 
among the simplest Protozoa, then in the Polyps and 
Corals, then in the Coelenterata, among which are the 
Medusae or jelly-fish. These, by the aid of diagrams, 
were shown to be fully equipped with sensory and motor 
nerves, and with a nerve centre to appreciate and act upon 
