page 274 note * It may be mentioned here that no second-case of a red-eyed Gammarus arising independently has occurred up to the present time (September, 1917), all the red-eyed animals used in the experiments being descendants of the original stock.

page 274 note † The term “Albino” is here used to designate those animals in which the eye possesses no coloured retinal pigment, but in which the chalk-white extra-retinal pigment is present. For eyes in which the coloured retinal pigment and the chalk-white extraretinal pigment are both absent we employ the term “colourless.”

page 276 note * We shall for convenience refer to the factor c, which on the hypothesis represents the absence of the colour factor C, as the “albino factor.”

page 277 note * Unless the young are examined and removed soon after they are extruded a certain number are lost through being eaten by the parents and the more delicate ones tend to disappear first. The albinos seem to be more delicate than the reds, and the reds than the blacks, so that unless the broods are counted within a short time the proportions of the different coloured eyes are liable to error. The figures given in the present paper include only such broods as were counted within forty-eight hours of the time of extrusion, unless the contrary is definitely stated.

page 277 note † Of these 589 red-eyed and 191 albinos came from the mating of one pair. (I.F. × I.E. Plate I, see p. 336).

page 279 note * Figures between brackets are also given under the other member of the pair and must therefore not be included in the totals.

page 292 note * Compare footnote p. 344. The exceptional numbers were specially noted at the time the brood was extruded, and there is no doubt as to the accuracy of the record.

page 294 note * This constitution was proved after Plato I was printed.

page 317 note * In all the animals referred to in this paper as “albino,” the eyes had the irregular, degenerate form figured on Plate VII, Fig. 4. If we take the view that, in the absence of red and black pigment, the regular form is in itself sufficient to distinguish the “all white” eye (Plate VII,.Fig. 7) from the imperfectly shaped “albino” eye, the following statement, the form of which we owe to Prof. R. C. Punnett, who has been good enough to read this paper in proof, puts the argument against our Hypothesis I in a brief form. The letter P must be understood to represent the factor for either red or black pigment, p the absence of such a factor. Hypothesis I. That two complementary colour factors are concerned, of which the “albino” female contains one, viz. P, and the “all white” male the other, viz. C.

Mated among themselves the chances of Pp zygotes coming together are 16 in 64, i.e. 1 in 4, and in such cases “all-white” eyes should appear in ratio 1:3. Amongst the blacks 109 such matings have been made, amongst the reds 40, and amongst the albinos 27, making a total of 176 such matings, and no “all-white” eyes of perfect form appeared. Hence Hypothesis I is not valid here.

page 342 note * In this section the word “normal-eyed” is used in the sense that the chalk-white extra-retinal pigment is present.

page 344 note * These totals are made up as follows:—

It will be seen that two of these families gave unexpected numbers.