XI. 
ANNIVERSARY ADDRESS. 
By the President, F. Maule Campbell, F.L.S., P.Z.S., etc. 
Delivered at the Annual Meeting, 2,2nd February , 1889, at Watford. 
Ladies and Gentlemen,— 
Will you allow me, as your President, on the completion of my 
term of office, to thank you for the unvarying kindness which I 
have at all times received at your hands, and to express my obli¬ 
gation to the officials of our Society, and more especially the 
Editor of our ‘ Transactions,’ for their hearty co-operation in my 
endeavours to perform the duties which you did me the honour to 
entrust to my care. 
The most natural course for me to take after my address of last 
year on “ The Means of Protection possessed by Plants ” would be 
to consider the analogous phenomena in animals. This would, 
however, involve a repetition of much which I had previously 
laid before the Society, and of many facts which are well known. 
I have chosen for my subject this evening —Structural Varia¬ 
tions in the Eyes oe Animals in reference to their Function. 
If succession of thought be advisable in the two addresses I 
have been called upon to make, it at least can be urged that the 
avoidance of danger by animals is greatly facilitated by the sense 
of sight. Further, the value of flight as a means of protection is 
much increased when sight enables the pursued to select from a 
distance a secure retreat. But quite apart from the consideration 
of the avoidance of enemies, locomotion is, under ordinary con¬ 
ditions, an essential requirement of any animal of fair size, for 
without such motion it could not obtain an adequate supply of 
food, and without sight it could not move in safety. Very minute 
animals do not require eyes any more than the plant Volvox globator , 
which is active in water. Animals without power of locomotion 
are eyeless, even when of some bulk, and an oyster, which is 
adherent to one spot during the whole of its imago existence, and 
which has its food brought to it by the medium in which it lives, 
could gain no more advantage from visual organs than a fixed 
plant, surrounded as it is by its pabulum of earth and atmosphere. 
Yet the plant is sensitive to light, and so are oysters, for they close 
their valves when the shadow of an approaching boat covers them. 
But we are referring to visual organs of some development, and 
the relations between them and locomotion are seen in the eyeless 
stationary mollusc which is the imago of a free-swimming larva 
with eyes. 
