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president’s address. 
in and all the tissues of the Caterpillar are developed into 
a feeding machine for the purpose of storing up nutriment. 
Then comes the most extraordinary change of all. When 
the Caterpillar changes to a Pupa or Chrysalis, the whole 
of the tissues of the body are broken up and converted 
into a milky but living pulp, and this is effected by means 
of phagocytes, or devouring cells, which are now known to 
play such an important part in the human body. These 
phagocytes literally eat up all the muscles, nerves, intestines, 
and air tubes of the Caterpillar and convert them into this 
milky pulp. This is, of course, a markedly retrogressive 
process. But now the turn of the imaginal cells comes. 
They commence growing and rapidly absorb the milky pulp. 
The wings can be detected in the embryo Butterfly, even in 
young Caterpillars ; but it is not till the pupa stage that they 
commence to grow rapidly. They are, at first, quite trans- 
parent, then opaque, and afterwards yellow or drab, and it 
is not till about twenty-four hours before the pupa hatches 
that the colours begin to show themselves. These are 
caused by minute scales, which are at first little bags 
filled with protoplasm, then this protoplasm is withdrawn 
and the scales are filled with air, and then finally the air is 
replaced by the blood of the pupa, and from this the colouring 
matter is secreted, but even then the complex process is not 
completed, for as I have already remarked, the peculiar 
gloss and sheen on the wings of many Butterflies are given 
by the refraction of light from the fine strise, which are 
formed on the surface of the scales, or by transmission 
through a layer of transparent cells which covers the whole 
wing. I have condensed this account from Wallace’s 
' World of Life,’ and he in turn has borrowed the facts 
from Mr. Lownes’ History of the development of the Blowfly 
and Mr. Mayer’s (an American entomologist) of the develop- 
ment of the wing scales of Butterflies and Moths. When we 
reflect on this marvellous series of changes, the development 
