206 THE KADIATING ORGANS OF THE DEEL* SEA FISHES. 



sally applicable, for we have found at least in one instance in Chauliodus — 

 and Leydig has found the same in other instances — organs, otherwise 

 identical with simple ocellar radiating ones, entirely enclosed in a pigment 

 sheath and therefore unable to radiate at all. 



The diversity is in fact so great that we are forced to assume that either 

 not all the organs described as radiating really emit ethereal waves, or if 

 they do, that the waves emitted by different organs are either differently 

 produced, or different in character, or both. Although direct observations 

 of the radiation of these organs are but few, we know (7) that some of them 

 at least do emit light, and (^) that the light emitted by different organs is 

 often different in color. 



It is remarkable that such observations have not been made more 

 frequently, and that Chun who took every deep sea fish caught immediately 

 to the photographic dark chamber, so often failed to observe any light 

 emitted from these organs. 



On the whole I should consider it most probable — although very far 

 from scientifically certain — that : (7) The organs produce a radiation. 

 (^) In the simple ocellar organs and the radiating discs this radiation is an 

 ethereal wave movement directly emitted into the surrounding water. 

 (S) In the compound ocellar organs this radiation is either also such a 

 movement or an emission of corpuscles (electron bombardment) and origi- 

 nates in the inner part. It is here not emitted directly into the surround- 

 ing water, but acts on the outer part and induces this to phosjihoresce and 

 emit ethereal waves. (4) The length of the ethereal waves thus directly 

 or indirectly produced by one and the same organ is always the same ; 

 that of the ethereal waves produced by different organs is often different. 

 {/)) In some cases the wave length lies within the visible part of the 

 spectrum; in other cases it may be smaller or greater, and then the radi- 

 ation is invisible. (6) The ethereal waves of the invisible radiations are 

 probably of greater length than those producing the red end of the 

 spectrum because such probably penetrate the water to greater distances 

 and because the remarkable telescopic eyes of some deep sea animals seem 

 to be peculiarly adapted to their perception. (7) These long ethereal waves 

 may (if not too long) be of the nature of (ultra red) light, or (if longer) of 

 the nature of electricity. 



