144 



IMIOSI'IIOKESCENCE 



however, more than compensated bv tlie wealth f 

 tlif r<rlenteratA. The common hydroid colony 

 Obflia ijfnicHlutu, often growing upon tin- fnnnU 

 ni l.uminaria ( Ma- tangle ), is a familiar instance. 

 Numerous Mcdiisir I jelly-fishes) must lie added tn 

 thr list : anil hen- tin- light is vaiiously cinilti'il ill 

 dinVieni -|.-ics: () from the whole surface; (6) 

 fruni tin' maiginal corpuscles ; (r)from the radial 



canal* : (</) fiom the ovaries. Soineii s (he .same 



gem;- includes IHII|I luminous ainl non luminous 

 forms MO-I l'i>nii;itiiliihe i .-I'll pen- 1 furnish in- 

 lances uf (he possession of this property : Mieh are 

 ilie long, reed like Kiiniciiliiia found in Loch Torri- 

 ilon (Ross shire) anil on other parts of the ScottUh 

 coast, ami reiiinitiihi. the subject of classic re- 

 searches by 1'jinceri, where the light emanates from 

 eight luinds or tiaet- "I -pccially modified ti.-sue 

 -ii uatcd in the wall of the KOOUMW. Alcyonarian-. 

 Siplionophores. ainl < 'lenophores also lunii-h con- 

 tributions to thi! list ; amongst these last the small 

 ovoiil jelly Iteroe was shown by Alliiian not to 

 mi it- light until it had remaineil for some 

 time in the dark. 



A lew species of Ophiuroids (hrittle stars) and 

 the deep-sea asteroid Odinia constitute the only 

 known instance- of luminosity aiming the Echino- 

 ilennatA, lint the worms furnish a larger array. 

 More than one case has len noticed among earth- 

 worms, the most complete description lieing due to 

 Professor (iianl. This worm ( Photodrilus) is 1J to 

 '1 inches long, and the luminous material is due to 

 cries of glands opening into the o'sophagus. In 

 these forms the luminosity ceases immeiliately 

 ufter sexual congress. Among the marine Chieto- 

 poda the (lower resides in the dorsal scales (elytra) 

 of the I'olvnoiihe. the tent-aclcs, dorsal tuliercles, 

 &c. of Chu'topterus, and the bunch of cephalic 

 tentacles oi" I'olvciiTUg, 



Of phosphorescent mollusca the small pelagic 

 Phyllirtu- iiiiri'iiltnlit is of ini|Mii-tance, because the 

 transparency of ii- tissues permits of its easv study 

 ami the successful localisation of it luminosity, 

 which is found to reside in nerve ganglia, 88 well 

 ax in certain small rounded cells situated at the 

 ends of the nerve twigs. The rock boring bivalve 

 (I'holas) is one of the longest known instances uf 

 animal phosphorescence, lieing recorded by I'liny, 

 who noticed that if any one chews the animal the 

 whole interior of his mouth U'comcs luminous. In 



this form the light is emitted fr five definite 



(Hitches all situated within the mantle cavity (1 )an 

 arc corresponding with the anterior margin of the 

 mantle, ( _'. :t i two triangular patches near the 

 ojiening of the branchial siphon, (4, 5) two Ion;,' 

 parallel bands \\ithin the same siphon. The 

 luminous material is -eereted by the epithelial 

 cells covering these (Millions of the Ixidy, and has 

 lii-eii shown lo consist essentially of two sulist-ances, 

 a white crystalline Inxly (lueifcrine) and a ferment 

 I Inciferasc) ; by the mixture of these two in a test- 

 tube it is possible to reproduce the light at will, 

 without the presence of living matter. The fer- 

 ment is most likely produced by a certain bacillus, 

 which occurs in large Btunbenln small pits in the 

 walls of the siphon. 



Inieiesting oWrvations upon bacilli as the cause 



of ptmpbomM have also liecn made on Cms 



tacea of the genera Talitrus and Orchestia (sand 

 hoppers) in a state of disease; the malady, and 

 the consei|iiont luminosiiy, can lie transferred to 

 healthy s|K>ciinens by inoculation, and the germs 

 IN- ream! in artificial media in tin- usual 

 manner. It would appear that the wind IIO|I|MTH 

 infect themselves with the bacilli from dea<l tish 

 on which they habitually feed. Many other < i n- 

 tarea, however, are luminous under normal condi- 

 tions, as, for instance, some Copepoda ( Sapphirina ), 

 and more particularly the Schi/opoda, one of which, 



li/iiinrs nun; ,/;,!. i- not nncomnion in the 

 deep waters of Loch Kync as well as on tlie Nm 

 wegian coast. Definite organs ( plioto-|ib,-ciia 

 here present for the pnslm-iion ot light ; one in the 

 stalk of each eye, one at the root of each lirsi. and 

 one at the root of each penultimate, thoracic limb, 

 and one under each of I lie lir-t four segments of the 

 alidonien. Each organ, as has Keen proved by 

 microscopic sections, is in reality a miniature bull's- 

 eye lantern, only equalled in eomple\ilv by the 

 organs of certain fishes. Sc\eial phosphon-- 

 Ascidians are known, the most conspicuous being 

 the jiclagic colony I'yrosoma, in which eacli individ- 

 ual zooiil has two loiinded luminous organs. The 

 researches of the recent deep-sea expedit ions i 

 revealed ipiile a large number of phosphorescent 

 fishes, with specialised organs of many ditlercnt 

 types. Some of these appear to IM- glandular, 

 whilst others are optical instruments of great com 

 ple\ity, with spheroidal and parabolic reflectors to 

 send tlie light in definite directions and with ! 

 t concentrate it. In some of the abyssal l.ophioids 

 ( angler- fish ) the modiliexl dorsal tin ray which acts 

 as a lure has a phosphorescent extremity, no doubt 

 to render it more attractive. 



There still remain for consideration the pirns- 

 phoreseent insert*, which belong almost exclusively 

 to the I!cmiptera( bugs) or the Colepptcra (lieetlc- 

 To the former lielong the lantern-flies ( Fulgoia and 

 allied genera), though it must tie mentioned that 

 the possession of this power by these insects lias 

 been denied by more than one good observer. 

 Luminous beetles appertain to the families Lam 

 pyridii- and Elateridie. The glow worm ( /.<iinf>i/ri'ii 

 \/,,i,i/,i/>i/(i) and the Italian firefly (Lurinln itnlica) 

 are goxl examples of tlie former, and have been 

 often described. In both cases the organs, which 

 are situated in a certain numlier of the posterior 

 segments of the alxlomcn. c.iii-ist of two layers, of 

 which the dorsal contains large quantities of uric 

 acid salts, and the ventral clear cells, which are 

 arranged in cylindrical lobules. In some species 

 lioth sexes are luminous, in others only one. In 

 the. Mexican firefly or Cucihos ( I'l/nyi/inrns iitirti- 

 I urn), which lielongs to the Elatend;e or click- 

 lieetles, the organs are three in number, one in 

 each upper anil hinder angle of the prothorax, and 

 one much larger occupying the centre of the ventral 

 surface of the tilst alidominal segment. This la-t 

 is invisible while the insect is at rest, but shim * 

 forth when it spreads its wings and raises its 

 alidoiiieii in flight, lloth the eggs and larvie of 

 this species are luminous. 



As regards the physical peculiarities of the lig'lit, 

 it varies in colour in different cases, being blue in 

 the mycelium growing in rotten wood, in Cunina, 

 llcroe. l'\ rosoma, and Lampyris : green in a .-]-, -ii- 

 of Agaric, I'icroeidcs, in I Ipbinroids, and in I'yro 

 phorus ; \ellow in Nix'tilnca. ISolina. anil with a 

 riildish tinge in a species of Cestnm; purple in 

 Kuniciilina and l''ulgora; whilst in PynfomQ 

 iitliiiiliriini and an . \ppendicularia observed by 

 (iiglioli it ha- I,,-, -n slated that the light varies in 

 colour. In all case- in which the matter has IK-CII 

 investigated the spectrum has liecn found to be 

 continuous; the amount of heat given oil in con- 

 nection with the process seems to be i|iiite infini- 

 tesimal, though actinic rays have liecn shown 

 to IK- pies,. nt. The phenomenon would appear 

 to consist in a definite vital process, which, in 

 the-e cases, leads to the production of radiant 

 energy just as in other instances to the evolution 

 of heat or of electricity. 



The uses of this property to its possessors may, 

 so far as is known at present, lie grouped under 

 four heads : (a) It enables the sexes to find each 

 other, as in Luciola and earthworms; (ft) it is 

 poatCMed by so many stinging Coelenteratea that 



