106 CLASS III. 
name the entire family of Medusxe Sea-Candles (Kandil el Bahr’). 
Bosc, and other writers after him, went too far when they main- 
tained that all Medusw, nay all Acalephes (EscHscHoLTz) are 
phosphorescent. Still, not Meduse alone, but other Acalephes also 
do possess this property: the phenomenon has been observed in 
species of Berot (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 Wri, for instance, saw Beroé ru- 
fescens emit a light after death, which differed by its bluish-green 
colour from the yellowish-red irradiations of the living animal. 
Dead Acalephe, 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 Meduse, like the 
species which Surtray named Noctiluca miliaris, and which, being 
not larger than a pin’s head, looks like a globule of mucus to the 
naked eye?. 
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 
Siphonophore 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 
HyNnpMAN, on the coast of Ireland, Diphyes®. Some species are 
widely diffused, as Aurelia aurita, and Cyanea capillata: the first was 
1 EerENBERG 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. 
2 [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. 102 ; HynpD- 
MAN Wote on the occurrence of the Genus Diphya on the coast of Ireland, Ann. of Nat. 
Hist. vit. 1841. p. 164. 
