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 proportions. 



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 after injection, sinus glands 

 of species of group III fail to do so.^^' ^^ This is so despite the fact that 

 Group III eyestalks are apparently as effective in lightening the bodies of 



