174 S - STILLMAN BERRY. 



Sasaki and other observers of Watasenia scintillans describe 

 the light of the large organs at the tips of the ventral arms as 

 purplish or Prussian blue, the body organs appearing "whiter 

 and less luminous" than these. In spite of their absolutely 

 different histological structure, the rays emanating from the 

 integumentary and subocular organs do not here appear to be 

 respectively distinguishable and one wonders whether, in this 

 regard, the observations recorded convey the whole truth. 



That such elaborate variety in the size, morphological detail, 

 and possession of accessory contrivances as will shortly be 

 described, must find at least partial expression in differences 

 in the physical qualities (intensity and color) of the resulting 

 light rays, seems as inescapable to the present writer as it did 

 to Chun (:O3a, p. 81). And on the whole the scanty evidence 

 just outlined is in accord, showing that the hues of the light are 

 different, often most strikingly so, not alone as between inde- 

 pendent species, but between the organs occupying different 

 situations on the body in one and the same species. 



6. DISTRIBUTION OF PHOTOPHORES ON ANIMAL. 



The photogenic function in cephalopods is, as has been seen, 

 not a general attribute of the body surface, but is always, so 

 far as is known, localized in the specialized tissue of definitely 

 circumscribed organs disposed in equally definite regions of the 

 body. It therefore becomes appropriate to examine what posi- 

 tion or positions on the body these structures have come to occupy. 

 Proceeding accordingly, one is at once struck with the fact that 

 although strong evidence of partiality for certain special situations 

 exists, yet no hard and fast rule may be laid down. The region 

 where the organs occur most commonly seems to be by all means 

 the surface of the ventral hemisphere of the eyeball. Photo- 

 phores are found in this position in most (probably all) of the 

 Cranchiidae, in Enoploleuthis , Abralia, Abraliopsis, Watasenia, 

 Asthenoteuthion, Pyroteuthis and Pterygioteuthis of the Enoplo- 

 teuthidae, in all the Lycoteuthidae, in Lampadioteuthis , in 

 Ctenopteryx, and in Chiroteuthis, at least some 25 and more prob- 

 ably around 29 of the entire 44 photogenic genera in the sub- 

 order Decapoda. Most of the cranchiid genera, comprising, so far 



