This proposition may be recognized as true in the case of _Deilephila_ also, if we compare the different species with one another as regards their ontogeny. We find here too that not only the sub-dorsal, that is, the phyletically oldest marking of the Sphingid caterpillars, occurs everywhere in the young stages, but also that it is being shunted back to younger and younger stages, in proportion to the degree of the development of the spot-marking reached in the full-grown caterpillar. Thus, for instance, in the caterpillar of _Deilephila euphorbiæ_ the highest form of spot-marking is reached, and in this species the sub-dorsal line is no longer the sole marking element at any stage. Leaving out of the question the absolutely unmarked little caterpillar which emerges from the egg (Fig. 118, _A_), there appears at once in the second stage a series of ring-spots connected by a fine white sub-dorsal line (Fig. 118, _B_). In the following stage, the third, this sub-dorsal line disappears without leaving a trace, and there remains only the spot-marking, which is subsequently duplicated. Let us compare with this the ontogeny of the bed-straw hawk-moth, _Deilephila galii_ (Fig. 117). The full-grown caterpillar possesses only a single row of ring-spots (_B_), and accordingly the young stages of the caterpillar up to the fourth show a distinct sub-dorsal line (_A_), although spots are seen upon it. A still earlier phyletic stage of development is illustrated by _Deilephila livornica_, in which the ring-spots are all connected by the sub-dorsal line. It can thus hardly be doubted that the biogenetic law is guiding us aright when we conclude from a comparison of the ontogeny of the different species of _Deilephila_, that the oldest ancestors of the genus possessed only the longitudinal stripes, and that from these small pieces were cut off as ring-spots, and that these were gradually perfected and ultimately duplicated, while at the same time the original marking, the longitudinal stripe, was shunted back further and further in the young stages, until it finally disappeared altogether.