TUNICATA. 311 
consideration, Only imagine from ten to twenty individuals, oval in 
form, more or less flattened, adhering by their dorsal surface to some 
submarine body, and connected together by their sides, so as to be 
shaped into the form of a star. ‘‘ When we excite one of the rays,” 
says Frédol, ‘‘a single mollusc contracts itself; when we touch the 
centre, they all seem to contract themselves (Cuvier). The buccal 
orifices are at the circumference of the star, but the intestinal ter- 
minations abut upon a common cavity, which occupies the centre of 
the star. Here we behold certain animals which eat separately, but 
which fulfil together as a community very singular functions—a kind 
of union and communism of which the moral world presents no 
prototype. With our molluscs we have a score of individuals united. 
We may consider the entire star as one single animal with many 
mouths. But, then, we have with it a luxury of organs for the 
function of intelligence which seeks and chooses, and parsimony of 
the organ of stupidity, which neither seeks nor chooses.” 
While the species of the genus Botryllus are fixed and adherent, 
those of the genus Pyrosoma, on the contrary, are oceanic. The animal 
colony which constitutes it floats and balances itself upon the waters, 
being capable of fully contracting and dilating itself. 
The name Pyrosoma has been given to these animals in con- 
sequence of their brilliant phosphorescent properties. According to 
the observations of Péron and Lesueur, nothing can exceed the 
brilliant and dazzling light emitted in the bosom of the ocean by these 
animals. From the manner in which the colonists dispose themselves, 
they form occasionally long trains of fire ; but it is a singular fact that 
this phosphorescence presents the same curious characteristics that 
are seen in the play of colours caused by the rapid movements of the 
cilia of the Beroé; namely, that the colours vary instantaneously, 
passing with wonderful rapidity from the most intense red to yellow, 
from golden colour to orange, to green, or to azure blue. Von 
Humboldt saw a flock of these brilliant living colonies floating by the 
side of his ship, and projecting circles of light having a radius of not 
less than twenty inches in diameter. He could see by this light the 
fishes which followed the ship’s track, during many nights, at the 
depth of from two to three fathoms. 
Bibra, a Brazilian navigator, having caught six Pyrosoma, employed 
them to light up his cabin. The light produced by these little 
creatures was so bright, that he could read to one of his friends the 
description he had written of these his living torches. 
Several species of Pyrosoma are known; P. elegans, about two 
or three inches in length, inhabits the Mediterranean ; 2. giganteum 
