If the foregoing view be accepted, there follows from it a fundamental difference between the development of the genera _Chærocampa_ and _Deilephila_. In the former the formation of the eye-spots proceeds from a subdorsal line, but they first appear on two of the front segments, and are then transferred to the _posterior_ segments. In _Deilephila_, on the other hand, a single ring-spot is formed on the penultimate segment bearing the caudal horn, and this is repeated on the _anterior_ segments by secondary transference. With respect to the origination of the ring-spot also, there is a distinction between this genus and _Chærocampa_, inasmuch as the first step towards the eye-formation in the latter consists in the separation of a curved portion of the subdorsal line, whilst in _Deilephila_ the nuclear spot first seems to originate and the separation of the mirror-spot from the subdorsal line appears to occur secondarily. It is difficult here to draw further conclusions, since the first appearance of the primary ring-spot has not yet been observed, and no more certain inference respecting the history of the formation of the _primary_ ring-spots can be drawn from the manner in which the _secondary_ ring-spots are formed. Because in _Hippophaës_ the formation of the secondary ring-spots begins with the red coloration of one or two shagreen-dots, it does not follow that the primary spot on the eleventh segment also originated in this manner; and this is not without importance when we are concerned with the causes which underlie the formation of ring-spots. In _Chærocampa_ also, the formation of the primary eye-spots appears to differ from that of the secondary--in the latter the black “ground-area” first appearing, and in the former the “mirror-spot.” The secondary eye-spots certainly remain rudimentary in this last genus, so that the evidence in support of this conclusion is thus much weakened; but it must be admitted that we are here on ground still too uncertain to admit of wider conclusions being based thereon.
As a final result of the investigation, we may advance the opinion that the existing species of the genus _Deilephila_ have reached five different phyletic stages, and that their very different external appearance is explained by their different phyletic ages; the appearance from these caterpillars of moths so extremely similar, can otherwise be scarcely understood.