This adaptation to the needles and twigs obviously explains why this caterpillar in the adult condition is so far removed from those of the genus _Sphinx_, while the moths are so nearly related that they were only separated as a distinct genus when we became acquainted with a large number of species. II. CONCLUSIONS FROM PHYLOGENY. The considerations previously set forth are entirely based on Fritz Müller’s and Haeckel’s view, that the development of the individual presents the ancestral history _in nuce_, the ontogeny being a condensed recapitulation of the phylogeny. Although this law is generally true--all recent investigations on development having given it fresh confirmation--it must not be forgotten that this “recapitulation” is not only considerably abbreviated, but may also be “falsified,” so that a searching examination into each particular case is very desirable. The question thus arises, in the first place, as to whether the markings of caterpillars, so distinct at the different stages of growth, are actually to be regarded as residual markings inherited from the parent-form; or whether their differences do not depend upon the fact that the caterpillar, in the course of growth, is exposed to different external conditions of life, to which it has adapted itself by assuming a different guise. The former is undoubtedly the case. It can by no means be denied that the conditions of life in young caterpillars are _sometimes_ different to those of the adults. It will, in fact, be shown later on, that in certain cases the assumption of a new guise at an advanced age actually depends upon adaptation to new conditions of life; but as a rule, the external conditions remain very similar during the development of the larva, as follows from the fact that a change of food-plant never takes place.[126] We should therefore rather expect a complete similarity of marking throughout the entire larval period, instead of the great differences which we actually observe.