198 PROFESSOR HUXLEY ON THE ANATOMY 



the other hand, if we open a Fyrosoma or Alcyonium, we find, among the adult individuals, 

 more or less developed emhryos, 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 ' M6- 

 moires,' Savigny forms the Pyrosomata into a family — the lAicice, containing one genus, 

 Fyrosoma, 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 eg^ before its extrusion." 



The Fyrosomata panlculata are species in which the animals are not verticillate, and 

 form very irregular circles, whose apices are everywhere irregularly projecting. This 

 division comprises F. glganteum and P. atlanticum. 



Fyrosoma 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 Fyrosomata 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 papiUse wide, 

 and for the most part obtuse. Diaphragm very narrow, and leaving a large aperture. 

 Total length 13-14 inches. 



h. Body bluish or a little violet, perfectly transparent. Papillae very narrow. No annular 

 diaphragm at the aperture, which presented only very young individuals. Total length 

 6 inches. 



c. Body bluish, perfectly transparent. Papilte longer and more pointed than in the 

 preceding varieties. An annular diaphragm, leaving but a very narrow aperture, around 

 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 Fyrosoma giganteum, Savigny gives some particulars not men- 

 tioned in his account quoted above. Thus, he says that the tunic offers but few vessels. 



