ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA = 319 
successively lodged between the intestine and the bottom of the 
tunic; there they continue to grow and to be developed, until their 
final expulsion. 
“In fact, we almost always find in this locality an isolated germ, 
which varies much in size. While small, it is only a perfectly white 
and transparent globule, in which a round aperture, like a mouth, is 
discernible ; when somewhat larger, this hollow globule already ex- 
hibits four little reddish spots ; and when larger still, these four spots 
have become a chain of four small but distinct little foetuses, which 
encircle the globule for three-fourths of its circumference. Lastly, 
when it has acquired its full size, the four foetuses, provided with all 
their organs, are united and form a complete ring. In this state it 
equals a third of the size of the individual which encloses it. It is, as 
-one sees, a new Pyrosoma already composed of four animals, and will 
very soon be independent of the large Pyrosoma in which it has 
originated. How does it escape? I know not. If, as is probable, it 
makes its exit by the same aperture as the excrements, this opening 
must be capable of undergoing excessive dilatation. 
“ These observations, taken in conjunction with those which I have 
made upon Botryllus, demonstrate that the corpuscles contained in the 
ovaries of these animals are compound germs, not intended for the 
growth of systems, but for their multiplication. On 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 ‘Mémoires, Savigny forms the 
Pyrosomata into a family—the Lucie, containing one genus, Pyrosoma, 
divided into two groups of species, P. vertzcellatum and P. paniculatum. 
In the former the animals are verticillate, or disposed in regular rings 
which project at intervals. It contains the single species Pyrosoma 
elegans, 15 lines long, with seven projecting rings, the first and the 
last terminal; the tuberosities composing the rings are lanceolate at 
‘tthe 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 :— 
“MM. Lesueur has observed, that the whorl which terminates the 
tube at its small end is formed by four tubercles, z.¢., 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 
