628 Natural History of Molluscous Animals : — 



the bivalves, are greatly so ; yet, for what purpose they light 

 up their gloomy ceils, unless it be to allure some minute in- 

 sect prey, it is hard to guess, for they themselves are " dark 

 in light." Pliny says, the phosphoric fluid is so abundant in 

 them, that it shines about the mouths of those who eat the 

 Dactyli, shines on their hands, and even on their clothes, 

 from drops falling thereon. (Hist. Nat., lib. ix. cap. 87.) The 

 Dactyli of Pliny have commonly been considered the same 

 as the Pholas Z)actylus of Linnaeus; but the description 

 given by the Roman naturalist will disturb no conjecture; 

 and his Z)actyli may very possibly be the ikfytilus lithophagus 

 (Lithodomus Cuvie?-), concerning which, Mr. Charles Ulysses 

 says, "that in the Bay of Naples the fishermen place the 

 animal in the sun, and with it besmear their hands and faces 

 at night, so as to illuminate them as with phosphorus." (Dill- 

 wyn's Cat. Rec. Shells, p. 303.) 



It is, however, among the Mollusca tunicata that the most 

 considerable phosphorescent species are found. The nomade 

 [roaming] tribes of this order abound in tropical seas ; and 

 there are few of them that do not light up their lamps in the 

 dusk. The iSalpae (or Dagysae of Banks, Jig. 109.) linked 



A portion of a chain of small Dagysae of the 

 natural size, and considerably magnified, to 

 show the course of the intestine : «, the mouth , 

 i, the anus. (From Home's Lect. on Comp. 

 Anat., VOL iL t. 73.) 



109 



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together in living chains, and the Pyrosomae, are the most 

 remarkable examples. Both genera appear to emit the 

 phosphoric flame only when the water is agitated, or when 

 they come in contact with opposing bodies, or when they 

 rise above the surface of the water. In his observations on 



