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president’s address. 
The practical importance of understanding the relation between 
Starfishes and Oysters may be realized by an estimate, quoted by 
Schiemenz, that the damage done by Starfishes to the Oyster-beds 
of Connecticut during the years 1887 — 1889 averaged half a million 
dollars annually, while that due to all other causes was less than 
a tenth of that amount. But my excuse for calling your attention 
to these facts is that we have here a forcible illustration of the 
utility of several structural features for which there is at first sight 
no obvious explanation. The temporarily internal condition of 
the shell of Natica. is shown to help it to withstand the attacks of 
Starfishes ; and the great development of the tube-feet in a Starfish 
is shown to have far more significance than would appear by 
assuming them to be merely organs of locomotion. It is hardly 
necessary to add that the theory of Natural Selection pre-supposes 
that the evolution of the organs of an animal has been directed by 
their utility to their possessor. 
The coloration of aquatic animals is a subject which is still very 
insufficiently explored. Many species are known to be coloured in 
a distinctive fashion, and in some of these cases it is believed that 
the colours are of the nature of protective colours or warning 
colours;* or that the pigments may have a respiratory value. 
The need of further observations on this subject is well 
shown by a consideration of the results arrived at by Messrs. 
F. W. Gamble and F. W. Keeble.f It is well known that certain 
Crustacea are variable in colour ; or that they can change their 
colour, an individual of certain species being under some conditions 
coloured in one way and under other conditions in another way. 
As examples of species which are known to change colour in- 
dividually, may be mentioned the common prawns Palaemon 
serratus and Pandalus annulicornis. One of the most variable 
species is Hippolyte varians, the subject of the memoir by Dr. 
Gamble and Mr. Keeble, a species commonly found in tide-pools 
*For a consideration of this subject in Nudibranchiate Molluscs see 
W. A. Herdman, Quart. Journ. Micr. Sci. vol. xxxi., 1890, p. 55. 
t “Hippolyte varians.- a Study in Colour-change,” Quart. Journ. Micr. Sci. 
vol. xliii., 1900, p. 589. A preliminary notice was published in Proc. Roy. 
Soc. vol. lxv., 1900, p. 4G1. 
