102 TUNICATA—SALPIANS CHAP, 
divided into two well-marked groups of species—(1) those such 
as S. (Cyclosalpa) pinnata, im which the alimentary canal is 
stretched out (“ ortho-enteric ” condition) along the ventral surface 
Fic. 61. —Salpa runci- 
nata -fusiformis. A, 
aggregated or ‘‘chain” 
form ; B, solitary form. 
At, Atrial aperture ; 
-at.m, atrial muscles ; 
Br, branchial aper- 
ture ; br.m, branchial 
muscles ; d./, dorsal 
lamina or “gill” ; d.t, 
dorsal tubercle ; emb, 
embryo ; end, endo- 
style; m, mantle ; 
m.b, muscle - bands ; 
n.g, werve - ganglion ; 
D-Ps peripharyngeal 
bands ; sf, stolon ; st”, 
“chain” of buds; 4, 
test ; v, visceral “ nu- 
cleus.” 
of the body, and (2) those such as 8. runcinata-fusiformis, in 
which the alimentary canal forms a compact globular mass (Fig. 
61, v), the “nucleus” (“caryo-enteric” condition), near the 
Fig. 62.— Diagram to show the arrange- 
ment and connexion of the aggregated 
zooids in a young chain of Salps. 1, 3, 5, 
zooids on the right; 2, 4, 6, zooids on 
the left. A¢, Atrial aperture of a zooid ; 
Sr, branchial aperture of another; c.t 
at the top of the figure points to three 
pairs of connecting tubes; c.¢ at the 
foot, to two pairs. Each zooid is united 
to each of the four neighbours it touches 
by a pair of connecting tubes, and so has 
eight such tubes in all. 
posterior end of the body. About fifteen species altogether are 
, known; they are all pelagic in habit, and are found in nearly 
all seas. Each species occurs in two forms (Fig. 61, A and B), 
the solitary asexual (proles solitaria), and the aggregated sexual 
(proles gregaria), which are in most species quite unlike one 
