SYSTEMATIC 
ARRANGEMENT OF TUNICATES. 
CLASS XI. 
TUNICATA, 
ANIMALS without distinct head, inclosed in an external covering 
coriaceous or membranous, and furnished with two apertures. A 
second tunic included in the former, perforated by two orifices cor- 
responding to the apertures of the external covering. Cibarious 
canal with mouth and anus internal, concealed. Respiration bran- 
chial, branchiz situated internally in front of the internal mouth or 
the commencement of the cesophagus, of different form in different 
cases, never divided into four lamine. Heart tubular, propelling 
the blood in a mutable direction. 
OrvDER I. Thaliacea. 
Body prismatico-cylindrical, with two apertures opposite, sub- 
terminal. Covering pellucid, thin, rigid. Animals swimming 
freely, drawing in the water by one aperture, expelling it by 
the other. ; 
Family I. Salpina. (Characters of the order those also of the 
single family.) 
Salpa Forsk., GMEL., Cuv., LAmM., species of Holothuria L. 
( Thalia Brown, BLUMENBACH, Dagysa BANKS and SOLAND., GMEL., 
Home). Branchiz extended obliquely through the internal cavity 
of body. Form in each species two-fold, the solitary progeny alter- 
nating with the associated. 
Comp. P. Forsk&t Descriptiones animaliwm, Hauniz, 1778, pp. 112— 
117; ejusd. Icon, Rem. natur. ibid. 1776, Tab. 35, 36; Cuv. Mém. (v. supra 
p- 691); A. Dz Cuamisso De Animalibus quibusdam e Classe vermium. 
Fasciculus 1. De Salpa. Berolini, 1819, 4t0; Mryen 1. 1.; EscHricut 
1. 1.; Kroun Observations sur la génération et le développement des Biphores, 
