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ANIMAL LUMINOUSNESS. 



eludes from his numerous observations on this 

 subject, that, in marine animals generally, the 

 coats of the stomach and intestines are the 

 light-giving organs. 



In insects the seat of luminousness is more 

 satisfactorily ascertained, and is found to vary 

 very much in different species and tribes. 

 The eggs of the lampyrides are said to be fre- 

 quently seen luminous, and to continue so for 

 several days after being deposited. In the 

 states of larva and chrysalis also, the same in- 

 sects emit light most vividly when touched, 

 chiefly from the posterior segments of the 

 body. On being much irritated, the whole of 

 the chrysalis seems to shine in a slight degree, 

 and for a short time. 



In the perfect female glow-worm of this 

 country, the light is emitted chiefly from the 

 inferior and lateral surfaces of the two or 

 three last segments of the abdomen. The 

 male of the same species presents only two 

 small luminous points on the sides of one of 

 the segments. When the light-giving surfaces 

 of the female lampyris noctiluca are narrowly 

 examined, it may be seen that, on the penul- 

 timate and antepenultimate segments, they pre- 

 sent bands of a bright greenish-yellow light, 

 which are abruptly terminated towards the 

 trunk by an irregularly waved line ; and that 

 from the rest of the same segments there 

 issues a fainter light of a pale green colour. 

 There is also a little light given out by the 

 posterior extremity of the dorsal line. In 

 L. itulica, the two last segments are wholly 

 and nearly equally luminous. Most of the 

 glow-worms in displaying their light recurve 

 their tails upon their backs, so as to bring their 

 luminous surfaces into view. 



Eluter noctilucm gives out light principally 

 from two points of the thorax, which are some- 

 what raised, and of an oval shape; but it lias 

 also two light-giving organs situated beneath 

 the wing-cases, which are not seen except 

 when the insect is flying. Light is also 

 emitted from the internal parts through the 

 interstices between the abdominal segments. 



In bupestris oce.llata, the light is emitted 

 from certain yellow spots upon the elytra : in 

 scarabceus phosphorictts from the belly : in 

 chlroscelis bifenestrata, (a New Holland insect) 

 from two oval, hairy, reddish spots on its 

 second ventral segment; while, in pausus splue- 

 rococcus, a dim phosphoric light issues from 

 its singular hollow globular antenna?. 



Macartney says that he always observed the 

 shining of scolopendra elcctrica to be accom- 

 panied by the appearance of an effusion of a 

 luminous fluid upon the surface of the animal, 

 paticularly about the head. On touching this, 

 his finger and other bodies received on their 

 surface a phosphoric light, which continued to 

 shine for a few seconds, and then died away; 

 and yet he could not see any actual moisture, 

 even upon smooth glass, although examined 

 immediately and attentively. 



The researches of Treviranus have led him 

 to conclude that there is no special luminous 

 organ in insects; but that the generally dif- 

 fused fatty matter is the seat of the function, 



by which the luminousness is produced. He 

 concludes, therefore, that, when the air has free 

 access to the interior of the body through the 

 respiratory tubes, the whole of the internal 

 organs give out light ; and that this is not seen, 

 excepting at certain points of the surface, 

 merely because the integuments are not trans- 

 lucent. 



V. Anatomy of light-giving organs. The 

 accounts of examinations of these organs that 

 have hitherto been published are rather imper- 

 fect. This appears to be owing chiefly to the 

 fact that the organs themselves are of very 

 simple structure and furnish no materials for 

 lengthened description. So much so are they 

 in insects, that one would be inclined readily 

 to conclude with Treviranus, that they are 

 nothing but the common fatty or interstitial 

 substance which fills up the bodies of insects, 

 slightly modified by the presence of some 

 phosphoric matter, were it not for the fact, 

 particularly observed by Macartney, that, in 

 the glow-worm, the luciferous organs are ab- 

 sorbed after the season for their use is past, 

 and their places supplied by the fatty sub- 

 stance. The following are the results obtained 

 by this naturalist and by Spix from their dis- 

 sections of the glow-worm, the fire-fly, and 

 the lantern-fly. 



In the glow-worm, there is spread over the 

 internal surface of the segments of the abdo- 

 men a yellowish substance of the consistence 

 of paste, which is thickest in the middle of 

 each segment, and terminates near each margin 

 by a wavy outline. It is of a closer texture 

 than the fatty matter, but otherwise resembles 

 it. Besides this substance, the last segment is 

 furnished internally, just beneath the most 

 transparent part of its integument, with two 

 small round bodies, lodged in depressions, 

 which contain yellow matter of more close and 

 homogeneous texture. Miiller and Murray 

 describe these round bodies as " two small 

 ovate sacs, composed of thready membranes, 

 and filled with a soft yellow pasty matter." 

 Under the microscope, they appeared to Macaire 

 to be composed of numerous branching fila- 

 ments, with minute granules adhering to them. 

 It is from points of the surface corresponding 

 to the situation of these round bodies that the 

 light is most constantly and most brightly 

 emitted. When dry, these luminous organs 

 have somewhat of the appearance of gum. 

 The dried matter is translucent and yellowish, 

 becomes darker on being kept, and appears to 

 be granular in its structure. Its specific gra- 

 vity is a little greater than that of water. 



In the fire-fly, the internal concavities of the 

 yellow spots of the corselet, whence the light 

 proceeds, are filled with a soft yellow sub- 

 stance, oval in shape, and of very uniform 

 consistence and density. This, under the mi- 

 croscope, appears to be formed of a large 

 number of very minute parts or lobules, closely 

 pressed together. Around these oval bodies, 

 the fatty matter of the corselet is arranged in 

 a radiated manner. Spix describes the same 

 organs as " yellowish glandular masses, into 

 which many branches of the trachea enter." 



