I02 



TUNICATA — SALPIANS 



CHAP. 



divided into two well-marked groups of species — (1) those such 

 as S. (Ci/closalpa) pinnata, in which the alimentary canal is 

 stretched out (" ortho-enteric " condition) along the ventral surface 



Fig. 61. — Salpa runci- 

 nata -fusiformis. A, 

 aggregated or "chain " 

 form ; B, solitary form. 

 A t, Atrial aperture ; 

 at.^n, atrial muscles ; 

 Br, branchial aper- 

 ture ; br.in, branchial 

 muscles ; d.l, dorsal 

 lamina or "gill" ; d.i, 

 dorsal tubercle ; eonb, 

 embryo ; end, endo- 

 style ; in, mantle ; 

 m.h, muscle - bands ; 

 n.g, nerve - ganglion ; 

 p.p, peripharyngeal 

 bands ; st, stolon ; st", 

 " chain " of buds ; t, 

 test ; V, visceral " nu- 

 cleus." 



;-.„at.m . 



of the body, and (2) those such as S. 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. At, Atrial aperture of a zooid ; 

 Br, branchial aperture of another; c.t 

 at the top of the figure points to three 

 pairs of connecting tubes ; c.t 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 {2}roles solitaria), and the aggregated sexual 

 (proles gregaria), which are in most species quite unlike one 



