570 HISTORY OF SYSTEMS. 



between the stars were filled with eggs of different sizes, " e.ach adhering by 

 one end to a very fine capillary filament. The smallest eggs are globular, 

 and as they advance in size, they change to an oval figure ; whence they 

 assume the shape of one of the radii of the stars." Ellis ascertained " that 

 each radius is a distinct animal by itself." Lib. cit. x. 671. — In his Essay 

 on Corallines, Ellis described another species, but his account of its structure 

 is very inaccurate. 



Pallas and Linnseus referred these species to the genus Alcyonium, under 

 a false view, evidently, of their organisation. Ga-rtner confirmed Ellis's 

 opinion that each ray of the star was a separate animal ; and, after a long- 

 interval, MM. Peron and Lesueur and M. Desmarest described one or more 

 other species, indicating their structure to be of higher complexity than other 

 polyjies, without, however, attempting to give them a proper position or 

 arrangement in the Animal Kingdom. For this great step in classification 

 we are entirely indebted to M. Savigny, who published his " Memoircs sur 

 les Animaux sans Vertebres" in 1816. 



His systematic table of the Tunicata is as follows : — 

 Animaux invertebres non articules. 

 Mollusques hermaphrodites et ace'phales. 



Class— ASCIDI^. 



Shell soft, formed by an exterior distinctly organised envelope, furnished 

 with two apertures, a branchial and an anal one. Cloak forming an interior 

 tunic, also furnished with two apertures corresponding with those of the 

 shell and adherent to them. Branc/iia occupying wholly or in part the sur- 

 face of a membi'anous cavity attached to the inner surface of the cloak. 

 Mouth without labial lamina?, and situated at the bottom of the respiiatory 

 cavity between the two branchiae. 



Order I. Ascidi^ Tethydes. 



Cloak adhering to the envelope or shell only by the two apertures. 

 Bianchia equal, large, forming the two side-walls of the respiratory cavity. 

 Branchial orifice furnished interiorly with a membranous and denticulated 

 ring, or with a circle of filaments. 



1. Family — TethYjE. 

 Bodi/ fixed. Apertures not opposite nor communicating by the cavity of 

 the branchife. Branchial cavity open at the superior extremity only, and its 

 aportin-e furnished with tentacular filaments. Branchict united or coalescent 

 on one side. 



I. SisiPLE Tethves. 



1. Section. Apertures with four rays. 



1. BoLTENiA. Body pedunculated. 



2. Cyntuia. Body sessile. 



2. Section. Apertures with more than four rays, or ivithout distinct rays. 



3. Phallusia. Body sessile. 



4. Clavelina. Body pedunculated. 



II. Compound Tethyes. 



3. Section. Both apertures with six regidar rays. 



5. DiAzoNA. Body sessile, orbicular ; a single system. 



6. DisTOMA. Body sessile, multiform ; systems "several, 



7. SiGiLLiNA. Body pedunculated, conical, vertical ; a 



single system. 



