PHYSIOLOGICAL LIGHT. 419 



Each organ is formed by a vesicle witk a transparent wall (rig-. 3, 

 luminous organ of the larva of Lampyra noctiluca, young specimen) 

 which is hyaline, anhistous, filled with very granular, polyhedric cells, 

 representing perhaps a post-embryonic blastoderm. There runs among 

 these cells a very finely ramified tracheal arborization. When the little 

 photogenic vesicle is compressed under tbe microscope there escapes 

 from it a liquid inclosing a multitude of small, rounded, protoplasmic 

 granulations, whose form and size recall those of certain spores; they 

 show active movements (Brownian 1 ?). 



This larval organ persists in the nympha, in the female, which pre- 

 serves until adult life its vermiform appearance, and in the male (fig. f>, 

 male organ) which in the state of a perfect insect is a winged beetle; 

 but it undergoes certain modifications. 



In the organ of the adult male, for example, there are more clearly 

 distinguished two layers, one whitish, opaque, chalky (fig. G, male 

 organ enlarged), formed of very refringent, crystalloid granulations, 

 the other parenchymatous, composed of granular, polyhedric cells. 

 The first layer is manifestly formed by the breaking down of the 

 parenchymatous cells, and by the change of part of the primitively 

 colloidal protoplasm to a crystalloidal state, as is clearly shown by fig. G, 

 which represents a vertical section of the male organ. This section 

 also shows some muscular fibers which are apparently for the purpose 

 of aiding the voluntary or reflex separation of the cretaceous layers 

 from the parenchymatous one. This is unquestionably the function of 

 these muscles in the female. 



Besides the larval organ, the female possesses two others which rest 

 upon the abdominal wall of the two penultimate rings, these remaining 

 transparent at this point (fig. 7, female organ). They are also com- 

 posed of two layers — one, superior, chalky, crystalloidal, the other 

 parenchymatous, formed of rounded cells arranged in regular, linear 

 series (fig. 8). 



Numerous tracheal ramifications carry on respiration in these organs, 

 and certain anatomists, who apparently had never seen any other lumi- 

 nous animals, have supposed these ramifications to be of primary 

 importance in the light-making mechanism, considering these tracheas 

 as blast tubes for enkindling the protoplasm as if it were charcoal. 

 But they should have at least known that the egg of the Lampyra has 

 no need for such an incendiary bellows to make it shine. We will 

 not dwell here upon the crudity of this interpretation that has 

 nothing physiological about it and whose error we have elsewhere 

 demonstrated. 



Between the files of cells of the female organs (fig. 8, e, c), there exist 

 numerous passages (me, me, me), whose width is regulated by the play 

 of the muscles (fig. .7, m, m, m), so that the blood may enter the organ 

 in greater or less quantity, thus rendering nutrition more or less 

 active. These muscles are under the control of voluntarv and reflex 



