W. C. M'Intosh on the Ahy»sal Theory of Light. 3 



great measure created for the supply and food of the more 

 perfect kinds.' " 



Phosphorescence, however, is a feature so broadly and 

 diversely distributed amongst marine animals, not only abys- 

 sal, but pelagic and littoral, that, on a careful view of the 

 subject, some objections to such a theory present themselves. 



On land the idea that the phosphorescence of certain insects 

 [Lampyris^ Elater, &c.) may guide them to their prey, was 

 early promulgated by entomologists (e. y. Kirby and Spence) . 

 Further, since the light in Lamjyyris is usually most brilliant 

 in the female, it has been connected with sexual characteris- 

 tics, especially as these females are wingless ; but it must be 

 remembered that both larva, pupa, and male are likewise 

 luminous. The provision, besides, continues after the repro- 

 ductive season. The luminous myriopods, again, show that 

 the presence or absence of wings has little to do with the 

 matter. Kirby and Spence have also observed that certain 

 insects can control their phosphorescence, in order, as they 

 suppose, to escape being captured by nocturnal birds. On the 

 whole, we can scarcely predicate of such animals, any more 

 than the botanists can with regard to the Fungi, that their 

 luminosity subserves them for the light of day. 



Amongst the inhabitants of the ocean, phosphorescence ap- 

 pears in all the invertebrate subkingdoms, from Protozoa to 

 Annulosa. Certain infusorial animalcules ( Ceratium^ Peridi- 

 nium, Synchceta) and the well-known Noctiluca are luminous. 

 Of Coelenterata there are Hydroid Zoophytes, true Medusa?, and 

 Alcyonaria ; while Pyrosoma and, it may be, others are simi- 

 larly provided among the mollusks. In the Annulosa, again, 

 there are Brittle-stars, PJavaricBj Annelids, and Crustacea. 



If, as the report says, luminosity subserves the purpose of 

 guiding animals to their prey, or of causing them to be preyed 

 upon (an unfortunate result), or even of illuminating the 

 abysses of the ocean, we should find traces of a general resem- 

 blance in habits, structm^e, or physiology, which would at 

 least indicate the bearings of a provision so important. Thus, 

 for instance, we should look for a similar state of matters 

 in the dark caves of lUyria and Dalmatia, or in those of 

 Kentucky. 



On surveying the marine animals possessed of this property 

 of phosphorescence, they are found to live under circumstances 

 so varied that it is truly difficult, not to say hazardous, to 

 attribute the function assigned in the report to the pheno- 

 menon. Thus Noctiluca miliaris occurs in such swarms as to 

 five the whole surface of the ocean a sparkling appearance, 

 lere blowing on the surface of sea-water taken at random 



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