Chromatophores and Color Change 697 



strom.*'^' *'■' This gland had been described earHer,"''- ^^' and at that time 

 was called the "blood gland." since it was then believed to be homologous 

 with a blood forming gland in the eyestalks of Crago, which Koller"" had 

 erroneously considered to be the source of the active principle. It was later 

 concluded that the glandular source of the active material could not pos- 

 sibly be the "blood gland," and it was renamed the sinus gland. This gland 

 has been found to exist in practically all of numerous malacostracan crusta- 

 ceans in which it has been sought, hence it is evidently of very general oc- 

 currence. Hanstrom, using eyestalkless specimens of Uca, Palaevwnetes, or 

 Penaens as animals for bioassay in his numerous experiments, found that 

 eyestalks of animals whose sinus glands were located in the head near the 

 brain CGehia and Hi^ipa [Emerita]') showed no chromatophorotropic activity. 

 When the eyestalks of other species were sectioned in various ways, the sec- 

 tions possessing the sinus gland always showed activity, other parts were al- 

 ways inactive. By utilizing the species differences in the anatomical arrange- 

 ment of eyestalk organs, Hanstrom was able to get, one by one, all the re- 

 maining organs of the evestalk into portions of the stalk showing inactivity. 

 Furthermore, no other structure in the stalk gave histological evidence of 

 having secretory activity except a glandular organ called the X-organ. Sec- 

 tions containing the X-organ, but not the sinus gland, were inactive; and 

 removal of the X-organ from eyestalks did not diminish their chromatophoro- 

 tropic activity. It was thus concluded that the sinus gland was the only eye- 

 stalk source of hormones influencing the red or black pigments in the test 

 animals employed. 



Hanstrom's conclusions were confirmed by Brown, ^^ who found that the 

 sinus glands could be removed and extracted by themselves, and that such 

 extracts possessed qualitatively and quantitatively, within experimental er- 

 ror, all the activity of total stalks, despite the fact that their volume was 

 only about 1 per cent of that of the stalk tissue (Fig. 264). Such extracts 

 elicited about 80 per cent of the activity of whole stalks for both Palae- 

 monetes red and Uca black chromatophores. Thus, for these two widely dif- 

 ferent chromatophore types, the sinus glands are the sole eyestalk source of 

 hormonal material. Furthermore, implantation of a sinus gland into the ven- 

 tral abdominal sinus results in a blanching of the animal which lasts about 

 100 times as long as the effects of an injection of extract that is the equival- 

 ent of approximately one gland. It has also been possible to remove the sinus 

 glands from the evestalks of Palaemonetes without substantial damage to 

 other parts of the eyestalk."'" Specimens after such removal show broad dis- 

 persion of their red pigment irrespective of background color, and extracts 

 later prepared from their eyestalks show no appreciable chromatophorotropic 



activity. 



The sinus glands of the eyestalks provide more than one chromatophoro- 

 tropin. This has been demonstrated by means of a comparative study of the 

 relative influences of extracts of the eyestalks of seven genera of crustaceans 

 in concentrating Palaemonetes red pigment and dispersing Uco black pig- 

 ment.-^^ The ratio of the effect on the two chromatophore types, influence on 

 Uca Black to influence on Palaemonetes Red, was called the U/P ratio. The 

 U/P ratios obtained for eyestalks or sinus glands from different sources va- 

 ried from one genus to another. For example, Crago sinus glands showed a 



