This constancy remains also in the following (fourth) stage, the caterpillar still being deep black, only the yellow (sulphur-coloured) lateral stripe, which has now become brighter, indicating the impending change (Fig. 67). This takes place in the fifth stage, in which the ground-colour suddenly becomes bright green, the black remaining at most only in traces on the anterior edges of the segments. This is the same marking as is shown by the fourth stage of the German form, only in this case individuals quite destitute of black do not occur. In many specimens indeed black forms the ground-colour, the green only appearing in certain spots (Figs. 71 to 75); in others the green predominates, and these two extremes are connected by innumerable intermediate forms, so that this stage must be regarded as the most variable of all. The sixth stage of the Genoese and the fifth of the German form have already been compared together. The results may be thus tabulated:-- _A. German form._ _B. Genoese form._ STAGE I. 9 days. 9 days. Black; constant. Black; constant. STAGE II. 8 days. 11 days. Black, with orange-yellow Black; constant. lateral stripe; variable. STAGE III. 5 days (in some 12 days. cases as much as 16 days). Black, with yellow; very Black, with orange-yellow variable. lateral stripes; constant. STAGE IV. 16 days (in some 6 days. cases only 5 days). Bright green and black, Black, with bright yellowish mixed; very variable. lateral stripe; constant. STAGE V. 6 days (frequently 6 days. longer). Dark green, with or without Bright green, small traces black bands; variable. of black; variable. STAGE VI. Pupation. 18 days. Bright green, without any black; constant. STAGE VII. Pupation. From this comparison we perceive that the process of transformation has at least become preliminarily concluded in the Genoese form. Why the backward transference of the newly-acquired character to the young stages has not yet occurred, or, at least, why it is not in progress, does not appear; neither can it be stated whether this will take place later, although we may venture to suppose that such will be the case. At first sight but a relatively short time appears necessary for the single stage V., which is still in a state of fluctuation (variable), to become constant by continued crossing, like all the other stages.