AND DISTRIBUTION OF THE FIROLIDA. | | 248 
float, and derive both the food which nourishes and the oxygen which vivifies them, if 
these changes are much beyond those limits which they are fitted to endure. "Those 
circulatory currents which exist in the Pacific and, indeed, all the great oceans probably 
serve, as a rule, to keep particular varieties in their native seas ; but when accidentally 
carried by branch streams into colder waters unsuited for their organization, then they 
doubtless die—a sequel which, as with animals of higher organization, perhaps most 
frequently results from external agencies; and with all that escape a violent end from 
predatory enemies, this is perhaps the usual cause and mode of death. 
We are equally ignorant of their distribution in depth; but the anatomical and 
physiological structure of all the known varieties shows that they are surface animals, 
and probably seldom extend more than a few yards below the sea-level, where the water 
is most highly oxygenated. Like most of the soft gelatinous animals caught by the 
towing-net, they avoid the heat and glare of the sun, and are generally entrapped at night, 
when they come to the surface to breathe and feed, this being doubtless their time of 
greatest activity, and day the period of repose, when they sink a moderate distance into a 
calmer, darker, and less sultry medium. 
In Plate XLIV. are outlines of the different varieties of Firolidæ caught by the writer 
in the Pacific during 1860 and 1861, in the regions indicated in the Table (p. 270) and 
Map. Fig. 20, Plate XLIV. was obtained in the South Indian Ocean during a subsequent 
voyage to Australia in 1864, and is evidently allied to and doubtless one of the Firoloid 
family, in which, however, no eyes, tentacles, tail, or very evident visceral nucleus could 
be seen; but which had a well-marked and large swimming-fin minus a sucker, a double 
envelope, consisting of an external hyaline coat, covering the entire body, and an internal 
muscular one, showing distinct transverse and longitudinal fibrillæ, similar to those 
described. Very active when caught, it was certainly not a mutilated Firola, as has been 
suggested with regard to Anops Peronii (D'Orb.); and we doubt if this least-developed 
group of the Firolidæ (Anops) is not one of real existence, though perhaps not so abun- 
dant as the others; for this is the only specimen met with, after long and systematic 
use of the towing-net, in the Atlantie, South-Indian, but especially the Pacific Ocean. 
These figures, sketched from life, are of the natural size. At least five of them, viz. 
figs. 14, 15, 17, 18, 20, appear to be new.  Carinaroides (Plate XLIV. fig. 16) is 
evidently identical with C. pedunculata, D'Orb. Voy., and Firoloides (Plate XLIV. 
fig. 19) with F. Keraudrenii, as indicated in the Table. The Map and Table show the | 
part of the Pacific where they are severally caught. Firoloides (Plate XLIV. figs. 13 and 
18), whose aetive and singular form renders it readily distinguishable, was met with 
thrice, and enjoys a wide range. Carinaroides (fig. 14) is easily known by its short 
deeply-keeled tail. In none of the Pacific varieties, except Carinaria (fig. 15), does the 
caudal appendage appear so lengthy and highly developed as in the Atlantic and 
. Mediterranean Firolidæ. Were observers to carefully keep their specimens (easily 
preserved in weak spirit), it would greatly facilitate correct classification, and obviate 
much error. des 
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