552 History of Luminescence 



The claim ot' penetrating radiation emitted by fireflies, made by 

 C. Henry (1896) and by H. Muraoka (1896), was later traced by 

 H. Muraoka and M. Kashya (1898) to chemical effects on a photo- 

 graphic plate, coming from material in the cardboard protecting the 

 plate from the light of the insects. 



HISTOLOGY 



The fine structure of the light organ of the firefly, which has 

 played such a prominent part in various theories of flashing, was 

 studied by Franz Leydig (1821-1908) and Albert von KoUiker (1817- 



1905) about the same time. In Leydig's Lehrbuch der vergleichende 

 Histologie des Menschen und der Tiere (1857) , the fat body and 

 the light organ of Lampyris splendidula are described and figured. 

 Leydig regarded the organ as a modified fat body but recognized 

 that the light substance was different from fat globules. KoUiker 



(1857, 1858) made one of the best early histological studies. He 

 pointed out that the organ was quite distinct from the fat body 

 and made up of two layers. There was an albuminous substance in 

 the lower layer and ammonium urate crystals in the upper layer. 

 As all tests for the element phosphorus were negative, KoUiker re- 

 garded the light as resulting from oxidation of albumin by the 

 nervous system. Since the work of Leydig and KoUiker, the histology 

 of glowworm and firefly lanterns has been a favorite material for 

 study. At least six more authors published on the subject during 

 the nineteenth, and sixteen during the first half of the twentieth 

 century. 



THE RAILROAD WORM 



Several other striking luminous beetles, which have excited the 

 admiration of naturalists, are closely allied to the lampyrid fireflies. 

 One of the most famous is the railroad worm of South America, so 

 called because of its double row of yellow lights, a pair on each 

 segment of the wingless body, with a red light on the head, thus 

 resembling a train illuminated at night. The animal is an adult 

 larviform female of the genus Phrixothrix, whose male is winged 

 and non-luminous. It was undoubtedly observed by Oviedo (see 

 Chap. II) , but then completely lost to science until Don Felix de 

 Azara (1809) again spoke of the insect during his travels in South 

 America, 1781 to 1801. He wrote (1: 214) : " I have seen in Para- 

 guay a great worm of about two inches length, in which the head 

 appears at night red and burning, and which has on each side 

 along its body a row of round spots resembling eyes from which 

 comes out a weak yellowish light." 



