82 KINETIC HORMONES — I 



ganglion", which presumably indicates the ganglionic-X-organ 

 as its source. 



The light- adapting hormone for the distal retinal pigment comes 

 from the same source as that which concentrates the red chromato- 

 phores of Palaemonetes (PLH § 3.223), and the two may be the 

 same, since they both appear to cause contraction of protein 

 molecules. Yet it requires 20 times as much crude extract to be 

 effective on the retinal cells as on the chromatophores (Kleinholz, 

 1942). 



Insecta. The distal retinal cells in the compound eyes of in- 

 sects can be divided into the same two types as in Crustacea; 

 but the means of controlling their pigment migration is not 

 known. 



3.223 Pigment movement in chromatophores 



There is an embarrassing w^ealth of detail about the so-called 

 chromatophorotrophic or chromactivating hormones from which 

 it is difficult to select representative examples. They are interesting 

 because they have similar physiological functions in both Crustacea 

 and the cold-blooded vertebrates, and because similar methods of 

 investigation have been applied to both groups, so that they can be 

 directly compared. 



Chromatophores are usually elaborately branched cells which 

 apparently remain stationary in the tissues, although they become 



Plate 3/1. Coloured photographs of the prawn, Leander serratus. 

 (a) Dorsal view of the cephalothorax to show the pattern formed by 

 the differentiation of the chromatophores into large red ones form- 

 ing the stripes, with small red and white ones between ( X 4). (b) Part 

 of the same, enlarged to show that there is more than one pigment 

 in each chromatophore ; the yellow component in the red chromato- 

 phores can be seen faintly and the central red component of the 

 reflecting, white chromatophore is clear. All are fully dispersed 

 ( X 50). (c) Two eyestalkless specimens kept on a white background, 

 on which red pigment becomes fully dispersed. Half an hour before 

 the photographs were taken each was injected with a different 

 fraction of an extract of the sinus gland. That given to the upper 

 specimen caused strong red pigment concentration; that given to 

 the lower specimen had no effect, {d) Part of the tail fan of a 

 specimen like the last, in which the maximum dispersion of red 

 pigment is shown (from Knowles, 1955). 



