Pyrosomatid^. ^MOLLUSCA. Pyrososia gioanteum. 
Family IV.— PYROSOMATIDyE. 
The Pyrosomas are compound animals; but instead 
of being fixed, they are free and floating on the surface 
of the ocean. 
Genus Pyrosoma. — This genus is the only one at 
present belonging to the famil}'. The common body 
of this peculiar genus ofTunicaries is semicartilaginous 
and noncontractile — the individuals of which the aggre- 
gate mass is composed forming a hollow cylinder from 
two to fourteen inches long, a half-inch to three inches in 
circumference, and open at one extremity only. These 
individuals are grouped in whirls each having two ori- 
fices, one at each end. They are united at the circum- 
ference of the middle portion by the fusion of the tests 
to one another into rings more or less regular, and 
varying in number according to the species, so that the 
whole forms the cylinder above described. — {Rupert 
Jones.') Their orifices are so arranged that the inhalant 
openings are external, the inhalant inside the tube ; and 
the result of so many little currents discharged into the 
cavity is to produce one general outflow, which impels 
the floating cylinder with its closed end foremost. — 
( Woodward.) The individuals composing this curious 
floating C3’]iader amount, in the adult Pyrosoma, to 
several thousands, forming, in fact, a numerous colony, 
each little molluskin its own cell, distinct, yet insepar- 
abl}^ connected with its fellows. The Pyrosomas are 
gregarious animals, and often occur in great numbers. 
They are found in the warmer parts of the great ocean, 
and at times they are so abundant in the Mediterranean 
that they have been found to clog the nets of the fisher 
men. Their delicate and transparent forms, and their 
elegant tints of colour, render them beautiful objects as 
seen floating during the day on the tranquil bosom of 
the sea; but their splendid phosphorescent property, 
the brilliant light which the}' give out at night as they 
glide past the vessel, have made them still more the 
objects of admiration to voyagers and naturalists. The 
descriptions given by many such are exceedingly inter- 
esting. The celebrated Humboldt, describing his 
having seen the P atlaniicum on his voyage to South 
America, says that it gave a light of a foot and a half 
in diameter while swimming beneath the surface. 
“ Only imagine,” he says, “ the superb spectacle which 
we enjoyed when in the evening, from six to eleven 
o’clock, a continuous band of those living globes of fire 
passed near our vessel. With the light which they 
diffused we could distinguish at a depth of fifteen feet 
the individuals of Thynnus, Pelamys, and Sardon, which 
have followed us these several weeks, notwithstanding 
the great celerity with which we have sailed.” Dr. G. 
Bennett, in his interesting “ Wanderings,” tells us that 
the vessel in which he was, continued, while proceeding 
at a rapid rate, during the whole night to pass through 
distinct but extensive fields of Pyrosomas, floating, and 
glowing as they floated, on all sides. Enveloped in a 
flame of bright phosphorescent light, he adds, and 
gleaming with a greenish lustre, these creatures seen 
at night, in vast shoals upwards of a mile in breadth, 
and stretching out till lost in the distance, present a 
spectacle the glory of which may be easily imagined. 
The vessel, as it cleaves the gleaming mass, throws up 
VoL. II. 105 
385 
strong flashes of light as if ploughing through liquid fire, 
which illuminates the hull, the sails, and the ropes with 
a strange unearthly radiance. M. Peron, the French 
naturalist, was, peihaps, the first who recorded this 
phosphorescent quality of the Pyrosomas. It was in a 
squall out at sea that his attention was called to the 
phenomenon. “ Suddenly,” he says, “ we discovered at 
some distance a great phosphorescent band stretched 
across the waves, and occupying an immense tract in 
advance of the ship. Heightened by the surrounding 
Fig. 232 
Pyrosoma giganteura. 
circumstances, the effect of this spectacle was romantic, 
imposing, sublime, rivetting the attention of all on 
board Soon we reached the illuminated tract, and 
perceived the prodigious brightness was certainly and 
only attributable to the presence of an innumerable 
multitude of largish animals floating with the waves. 
From their swimming at different depths they took, 
apparently, difl'erent forms; those at the greatest depth 
