198 PROFESSOR HUXLEY ON THE ANATOMY 
the other hand, if we open a Pyrosoma or Alcyonium, we find, among the adult individuals, 
more or less developed embryos, which can only have proceeded from simple germs whose 
existence is manifested successively. These last, then, were all contained in the compound 
and primitive germ." 
It is obvious from the last paragraph that Savigny was unaware of the origin of the 
latter ' embryos * by gemmation. In the < Systeme des Ascidies ' appended to the • Me- 
moires,' Savigny forms the Pyrosomata into a family— the Lucia, containing one genus, 
Pyrosoma, divided into two groups of species, P. verticillatum and P. paniculatum. In the 
former the animals are verticillate, or disposed in regular rings which project at intervals. 
It contains the single species Fyrosoma elegans, 15 lines long, with seven projecting rings, 
the first and the last terminal ; the tuberosities composing the rings are lanceolate at the 
ends. There is no annular diaphragm around the wide mouth of the tube. It inhabits 
the Mediterranean, near Nice. Under the head of this species, Savigny makes the 
following important remark : 
" M. Lesueur has observed, that the whorl which terminates the tube at its small end 
is formed by four tubercles, i. e. by four animals. He thinks that this disposition is 
peculiar to the species in question ; but, with a little attention, the same arrangement is 
to be found in the following species, where these four animals seem to be the representa- 
tives of the four little foetuses which are developed in the egg before its extrusion." 
The Pyrosomata paniculata are species in which the animals are not verticillate, and 
form very irregular circles, whose apices are everywhere irregularly projecting. This 
division comprises P. giganteum and P. atlanticum. 
Pyrosoma giganteum has an almost cylindrical body, the external tuberosities being 
very unequal, hemispherical or conical; the most projecting having their appendage 
or terminal papilla lanceolate, subcarinate, and finely denticulated. The opening of the 
tube is commonly narrowed by an annular diaphragm. The total length of the largest 
tubes is 14 inches ; the opening, including the diaphragm, is 2 inches across ; the indi- 
viduals vary in size from 3-5 lines, according as the neck of the thorax is more or less 
prolonged — a circumstance which is independent of the age of the individual. , 
The Pyrosomata of this species presented several varieties : — 
a. Body strongly stained with brown, as well internally as externally, apparently in 
consequence of a brown substance filling the branchial cavities. Terminal papillae wide, 
and for the most part obtuse. Diaphragm very narrow, and leaving a large aperture. 
Total length 13-14 inches. 
b. Body bluish or a little violet, perfectly transparent. Papillae very narrow. No annular 
diaphragm at the aperture, which presented only very young individuals. Total leng 
6 inches. 
c. Body bluish, perfectly transparent. Papillae longer and more pointed than in the 
preceding varieties. An annular diaphragm, leaving but a very narrow aperture, aroun 
which almost all the animals were adult. Total length 5, 6, 7 inches. 
This species inhabits the Mediterranean and Atlantic, bordering the French coasts. 
In the description of Pyrosoma giganteum, Savigny gives some particulars not men- 
tioned in his account quoted above. Thus, he says that the tunic offers but few vessels, 
