LIGHT PRODUCTION IN CEPHALOPODS. 173 



Of the subsequent observations, only a few trouble to specify 

 the apparent color of the light rays. I use the word apparent 

 advisedly, not alone because of the ever-present subjective 

 considerations by which one and the same ray may yield diverse 

 impressions to different persons at the same time and under the 

 same conditions, or to the same person at different times or 

 under different conditions, but also because there is evidence that 

 the original color values of the light rays may suffer modification, 

 either by reason of the physical features of some of the super^ 

 vening tissues of the photophore itself, or by the interposition of 

 the chromatophoric color screens to which attention has already 

 been drawn. 



The extent to which the brilliantly varied illumination which 

 was described by Chun for Lycoteuthis diadema is due to such 

 considerations as these, rather than to differences inherent in 

 the light rays produced by the respective organs is therefore a 

 matter for considerable speculation. In this species Chun 

 (:O3, pp. 569-570; :o3a, p. 81; :io, p. 50) described the light of 

 the central organ in each subocular series as "marvelous ultra- 

 marine blue," of the anterior axial organ as "sky blue," of the 

 two anal organs as "ruby red," of the remaining organs as 

 "snow-white" or "pearly." But it should be remembered that 

 no matter what other rays may have suffered absorption to 

 result in the described effect on the human eye, no sort of screen 

 or filter could manufacture those which evidenced themselves and 

 they must therefore have been produced within the photogenic 

 tissues. If, as in all other luminous organisms which have been 

 subjected to examination, this is still a relatively efficient and 

 therefore "cold" light, the question is yet before us whether 

 the "ruby red" rays of Lycoteuthis are none the less as "cold" 

 as the ultramarine and blue ones, or as the blue-green lumines- 

 cence of the firefly. The biochemist and biophysicist have here a 

 tempting field, once the technical biological difficulties of securing 

 and handling the animals can be fairly overcome. 



The light of the luminous secretion of Heteroteuthis dispar is 

 described by Meyer (:o6, p. 389) as "pale greenish," and by 

 Dahlgren (:i6, p. 71) as "the usual blue-green of luciferine when 

 burning outside the body." 



