. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 698 Comparative Animal Physiology relatively high value, whereas those of Palaemonetes showed a relatively low value. Uca yielded an intermediate value. The order for the seven species investioated showed no correlation with either the sizes of the animals or the relative potencies as assayed on Uca. The hypothesis proposed to explain these data, namely, that sinus glands differed from one another in the pro- portions of two 'principles, (1) a factor predominantly darkening Uca (UDH), and (2) a factor predominan
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 698 Comparative Animal Physiology relatively high value, whereas those of Palaemonetes showed a relatively low value. Uca yielded an intermediate value. The order for the seven species investioated showed no correlation with either the sizes of the animals or the relative potencies as assayed on Uca. The hypothesis proposed to explain these data, namely, that sinus glands differed from one another in the pro- portions of two 'principles, (1) a factor predominantly darkening Uca (UDH), and (2) a factor predominantly lightening Palaemonetes (PLH), was oiven strong support by the discovery that the sinus glands of each spe- cies yielded two active fractions, one alcohol-soluble and the other alcohol- insoluble. The former gave a very low U/P ratio, as if possessing a larger proportion of PLH, and the latter gave a high U/P ratio, suggesting a larger proportion of UDH. It was possible to restore the initial U/P ratio for the gland of a species simply by recombining the two fractions. These re- sults lead to only one possible conclusion, namely, that the eyestalks of all seven species investigated, representing examples of Groups I. II. and III, possess two chromatophorotropins in differing TIME IN HOURS Fig. 264. Change in the average state of black pigment dispersion in eyestalkless Uca (A) and red pigment concentration in eyestalkless Palaemonetes (B), after injection of equal doses of extracts of whole eyestalks (broken line) and extracts of sinus gland (solid line) in equal numbers per unit volume of extracting medium. From Brown.^ The sinus glands of the crustaceans of Group III so far examined lack one principle present in the glands of species of Groups I and II. This has been established through the discovery that, whereas extracts of the eye- stalks or sinus glands of species of Group I or II will lighten the telson and uropods of Crago within three or four minutes
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