of the process of development must therefore have given them a still
greater preponderance over their fellows, and the effacing of the
metamorphosis must have gone on more rapidly. What has taken place in
each individual case, whether the species has immigrated after it had
lost the metamorphosis, or lost the metamorphosis after its immigration,
will not always be easy to decide. When there are marine allies without,
or with only a slight metamorphosis, like the Lobster as the cousin of
the Cray-fish, we may take up the former supposition; when allies with a
metamorphosis still live upon the land or in fresh water, as in the case
of Gecarcinus, we may adopt the latter.

That besides this gradual extinction of the primitive history, a
FALSIFICATION of the record preserved in the developmental history takes
place by means of the struggle for existence which the free-living young
states have to undergo, requires no further exposition. For it is
perfectly evident that the struggle for existence and natural selection
combined with this, must act in the same way, in change and development,
upon larvae which have to provide for themselves, as upon adult animals.
The changes of the larvae, independent of the progress of the adult
animal, will become the more considerable, the longer the duration of
the life of the larva in comparison to that of the adult animal, the
greater the difference in their mode of life, and the more sharply
marked the division of labour between the different stages of
development. These processes have to a certain extent an action opposed
to the gradual extinction of the primitive history; they increase the
differences between the individual stages of development, and it will be
easily seen how even a straightforward course of development may be
again converted by them into a development with metamorphosis. By this
means many, and it seems to me valid reasons may be brought up in favour
of the opinion that the most ancient Insects approached more nearly to