NOTES ON THE PHOTOPHORES OF SEKGESTES PREHENSIL1S BATE. 303 



the morning following the night when the specimens were collected, that 

 is to say, after they had been kept alive in captivity for about ten 

 hours. I greatly regret that circumstances prevented me from doing the 

 fixing work on the sea, right at once after the capture. The fact already 

 alluded to, that in some photopores the photogenous cells are found in the 

 process of breaking up, may be due to the belated fixing of the material. 

 Nevertheless, there are to be found in the fixed material a goodly number 

 of other photophores, which seem from their histological appearance to have 

 remained in a state fairly well representing their normal structure. 



A completely developed photophore of 6*. prcliensilis may be said to be 

 composed of the following eight parts : 1) the lens, 2) the lens epithelium, 

 3) the photogenous layer, 4) the basement membrane, 5) the reflector, 6) 

 the pigment mantle, 7) the connective tissue theca, and 8) the nerves. 



1) The lens. — This is nothing more than a strongly thickened areolet 

 of the general cuticula. The latter, perfectly colorless and transparent in all 



parts of the body, 

 is made up of three 

 layers, of which 

 the middle and the 



inner are about 



equally thick, while 

 the outer is by far 

 much thinner than 



either 



and 



re- 



Fig. I. Semi-diagrammatic representation of a section 

 through the median photophore of a thoracic sterilite. 

 Pigments omitted. X400. From a transverse section of 

 S. preheiisilis. bin, basement membrane; cs, connective 

 strands of photogenous layer; hy, hypodermis; l\, covering 

 layer of lens; /«> outer lens body; / 3 , inner lens body; le, lens 

 epithelium; 11, nerve; p/i, photogenous cells; pi, pigment 

 layer; r, reflector; ih, theca. 



presents a fine 

 membrane of only 

 about I \ [J. thick- 

 ness. Now, the 

 photophore lens 

 consists of three 

 parts correspond- 

 ing to, and directly 



