106 CLASS III. 



name the entire family of Medusae Sea- Candles (Kandil el Bahr 1 ). 

 Bosc, and other writers after him, went too far when they main- 

 tained that all Medusa, nay all Acalephes (EscHSCHOLTz) are 

 phosphorescent. Still, not Medusse alone, but other Acalephes also 

 do possess this property : the phenomenon has been observed in 

 species of Beroe ( Cydippe pileus, Eucharis multicornis, &c.) : Ste- 

 phanomia also diffuses a lively light by night. This phosphorescence 

 is a vital phenomenon, and ceases on the death of the animals : 

 though some of them, like other organic substances, are luminous 

 even after death ; but that light is of a different nature from phos- 

 phorescence during life. Thus WILL, for instance, saw Beroe ru- 

 fescens emit a light after death, which differed by its bluish-green 

 colour from the yellowish-red irradiations of the living animal. 

 Dead Acalephce, or mucus arising from decomposition of animal sub- 

 stances, can contribute little or nothing to the gorgeous spectacle 

 of the illumination of the sea, of which so many voyagers have 

 given striking descriptions : the chief cause of the brilliant sparks 

 resides in minute marine animals, especially Medusae, like the 

 species which SURIRAY named Noctiluca miliaris, and which, being 

 not larger than a pin's head, looks like a globule of mucus to the 

 naked eye 2 . 



Acalephes are met with in all seas. A very large number of 

 species occur in the Mediterranean belonging to the most different 

 forms. In the seas of the cold and temperate zones scarcely any 

 Siphonophorce are found, at least not in the northern hemisphere ; 

 however the currents may occasionally bring with them southern 

 forms from a distance, as is proved by the fact that OWEN, on the 

 south-west coast of England, observed Velella and Porpita, and 

 HYNDMAN, on the coast of Ireland, Diphyes 3 . Some species are 

 widely diffused, asAurelia aurita, and Cyancea capillata: the first was 



1 EHBENBERG das Leuchten des Meeres, s. 146. Comp. especially on this subject 

 the work already quoted p. 53, so instructive as well from the author's own observa- 

 tions as from the extensive use he has made of earlier works. 



3 [VAN BENEDEN refers Noctiluca miliaris not to the Acalephes but rather to 

 the Rhizopoda; see note by Dr SCHLEGEL in the german translation of this work, 

 p. 106.] 



3 OWEN Lectures on the comp. Anat. of the invertebr. Animals, 1843, P- IO2 ; HYND- 

 MAN Note on the occurrence of the Genus Diphya on the coast of Ireland, Ann. of Nat. 

 Hist. vii. 1841. p. 164. 



