6 TRANSFORMATIONS OF INSECTS. 
to sharks and whales, and to turn into something much more 
dissimilar than butterflies are to caterpillars—into barnacles. 
Instead of their development progressing during the metamor- 
phosis it retrogrades, and the adult creature is less perfect 
than the young. 
Swammerdam, the great Dutch naturalist of the 17th century, 
laboured to prove that the structural elements of the perfect insect 
were already within the caterpillar or larva, and he impressed upon 
his contemporaries and upon many of his successors that all the 
parts of the adult were in the creature as it escaped from the egg, 
but on a small scale. He considered that the glories of the fully- 
developed insect were masked in the tiny grub, and hence the 
name of larva. But careful anatomical researches and dissections, 
with the aid of the microscope, gradually disproved this idea of 
Swammerdam’s, and by the beginning of this century the 
opinions of naturalists concerning the nature of the metamor- 
phoses of the Articudata were much nearer the truth. 
It had become known that some important organs which 
existed at one period of insect life were not to be found at others, 
and that new combinations of structures having peculiar functions 
and uses appeared during growth. 
Every one knows that a young chicken differs in shape from 
one just hatched. Now, the anatomists of the early part of this 
century laboured at the investigation of the alterations in the 
arrangement of the internal parts and organs which took place 
during the egg life of the bird, and they proved that the develop- 
ment within the egg was akin to that which entomologists were 
obtaining dim notions about with respect to the metamorphoses 
of insects. Later still) Von Baer and Rathke asserted that the 
early condition within the egg—the embryo—of all animals, had 
one aspect, but that soon essential differences in structure com- 
menced, and determined the future shape and peculiarities of the 
adults. This is not consistent with modern research, nor is it 
true that the most important organs appear first of all in the 
earliest stages of life; but these theories had excellent effects 
upon the progress of science. And Milne-Edwards proved that 
the embryos of the kinds of Crustacea, which, when fully grown, 
are of the same genera or groups of species, resembled each 
