president’s address. 167 1 
is one, which I am sorry to say, cannot be illustrated by the 
specimens before me, but which must necessarily come under 
the notice of any one engaged in forming a collection of 
Butterflies and Moths. I mean the wonderful transformation 
which takes place during the life of a lepidopterous insect. 
Of course, the bare facts of these transformations, viz., the 
change of Caterpillars into Chrysalises and of Chrysalises 
into perfect insects are known to every one ; but the details 
in the process, which have been brought to light by recent 
research, only render it more wonderful than ever. The 
oldest insects in point of geological time are the Cockroaches 
and their allies, and these undergo the least change in process 
of growth. They emerge from the eggs with rudimentary 
wings, and after a succession of moults perfect wings are 
acquired ; but there is no great change in the appearance of 
the insect during life. In the case of the Lepidoptera, how- 
ever, the transformation scenes are complete. It is impossible 
to conceive of creatures more unlike each other than the 
Caterpillar and the Butterfly. The Caterpillar is a worm-like 
animal, adapted entirely for feeding and storing up nutriment. 
Its powers of locomotion are limited, and it has no organs 
of reproduction. It is essentially of the earth, earthy. 
The Butterfly, on the other hand, is an airy creature endowed 
with remarkable powers of motion, and capable of crossing 
considerable stretches of sea. It is in many cases painted 
with all the colours of the rainbow, and is endowed with powers 
of propagating its species. At the same time, its digestive 
organs are very attenuated, and it never increases in size. 
Now the change from the Caterpillar to the Butterfly would 
seem to be effected by a double process of progression 
and retrogression going at the same time. According to 
Weismann, certain cells are found in the egg, which he calls 
imaginal discs, and which are the rudiments of the Butterfly. 
These remain unaltered during the whole life of a Caterpillar, 
and a process, of what may be termed retrogression, sets 
