Ko.544] SHORTER ARTICLES AND DISCUSSION 



245 



under natural conditions, but as I shall attempt to show later 

 neither temperature differences nor different rates of develop- 

 ment materially influenced the amount of pigment developed. 



The animals were fed on alternate days with an abundance 

 of daphnids and cyclops, and later with small bits of tender 

 beef. The amount of pigment developed was judged by making 

 accurate determinations of the color of two definite regions of 

 the skin of each individual. For the body color, determinations 

 were made for a region to one side of the median line and about 

 midway between the pectoral and pelvic limbs. This is the 

 most heavily pigmented region of the larva. For the head 

 color the region immediately anterior to a line from one eye 

 to the other was used. This is usually the least pigmented por- 

 tion of the animal. The colors were obtained by means of the 

 Milton Bradley color tops and the records made in percentages 

 of black, white, orange and yellow, which when blended most 

 nearly matched the color of the skin of the animal. The orange 

 used in these tops most nearly resembles the No. 101 of 

 Klincksieck et Valette's "Code des couleurs" and the yellow 

 is intermediate between Nos. 206 and 211. All the color records 

 under consideration for Series A and B were made within two 

 weeks and under uniform conditions so that the results ought 

 to be strictly comparable. The records for the somewhat more 

 rapidly developing Series C were made about three weeks 

 earlier. The results tabulated include color records for all the 

 surviving individuals of Series A and B and sixteen individuals 

 selected at random to constitute Series C. 



The average body color of the Series A, numbering 22 indi- 

 viduals, reared in the cave, contained 49.7 per cent, of black, 

 16.9 per cent, white, 9.3 per cent, orange and 24.1 per cent, 

 of yellow ; or 49.7 per cent, black and 50.3 per cent, non-black. 

 The extreme range in degree of pigmentation was from 32 black 

 and 68 non-black to, in the case of one individual decidedly 

 darker than its fellows, 70.5 black to 29.5 non-black. The 

 average head color was 38 per cent, black and 62 per cent, non- 

 black (26.7 white, 7.0 orange and 28.3 yellow) with 27 per 

 cent, and 51 per cent, as the extremes in amounts of black. 



On the average, Series B (7 individuals), reared in labora- 

 tory light, had a body color of 86.1 per cent, black and 13.9 per 

 cent, non-black (4.7 white, 2.4 orange and 6.8 yellow), ( and a 

 head color of 76.1 per cent, black and 23.9 per cent, non-black 

 (8.4 white, 4.0 orange and 11.5 yellow). The range for the 

 body color was from 82 to 90.5 black and for the head color 



