£4 Animal cular Phofpborefcence of Ocean Water, 



or vena cava, whence the eight arteries before mentioned 

 derived their fupply. 



Such being the manner in which their juices circulated, 

 it could now be underftood in what part the luminous exhi- 

 bition was made. I was foon fatistlcd it was in the arteries, 

 and not in the veins; and the diaphanous confidence of the 

 animal permitted this light to be feen through its fubftanoe 

 as plain as through cryftal. The blood, after entering the 

 arteries, and during its fubjection to their action, became 

 luminous, and palled through like ftreams of ignited metal or 

 electric emanations. And this vafcular illumination, vari- 

 outly refracted in pafling through the pellucid fubftance of 

 the creature, through the water in which it floated, and 

 through the atmofphere to the eye, made the whole body, 

 when feen at a diftance, appear luminous. Thefe ftreams of 

 light, however, were not conftant. They not only intermitted 

 when the circulation of the blood was intermitted, and the 

 action of the vefTels flopped ; but very commonly, while the 

 fluids were pafling through their tubes with the utmoft ra- 

 pidity, there would be no phofphorefcence at all : then, 

 again, one or more, and fometimes all the arteries, would 

 fuddenly exhibit the lucid phenomenon, and the creature 

 and the furroundihg water nalh with light. This luminous 

 evolution was not confined to the nocturnal exiftence of the 

 animal $ for, on attentively examining their functions by 

 day, when the light was too faint to be {ccn, it could be 

 eafily diftinguifhec|, by the colour of the fluid in the veflels, 

 that the fame action was going on. It appeared of a blueifh, 

 or fomewhat iridefcent hue, along the courfe of the arteries, 

 though its feebler light, like that of a taper, was loft amid 

 the fplendour of the folar rays. The fame procefs, however, 

 is going on during the day-time, in thefe creatures, though 

 unobferved, that we behold in the dark. 



One of thefe medufas may be compared to a glafs lanthorn, 

 freely permitting the light produced within it to difiufe itfelf 

 to the furrouncTing fpaces, while an external obferver can 

 thereby difcern what is going on in the infkle. I am fo en- 

 tirely fatisfied of the connection between this evolution of 

 Jight and the circulation of arterious blood, that I want nq 

 clearer evidence to that point. It is probable that in an ani- 

 mal which is entirely deftitute of lungs as well as of heart, 

 the pulmonary function may be performed by the vital veflels 

 themfelves. la thefe creatures 1 believe this to be the fact. 



The light, then, which thefe marine animals exhibit, may 

 be concluded to be produced by a function in them analogous 



