III SALPA—_STRUCTURE 105 
most cases a retina formed of elongated cells, and a pigment-layer 
placed upon the ganglion. 
The so-called otocysts of Salpa have been shown by Metcalf 
to be really glandular organs. They have been called lateral 
neural glands; they do not open at the dorsal tubercle, but 
separately into the pharynx. These lateral neural tubular glands 
have also been regarded as nephridia. 
The large spaces at the sides of the dorsal lamina (often 
sgl mus. bds 
Rm ee 2 ct ng fi 
ot 
at.m 
a) 
\.. SLO 
tes t! 
al i < ht in t 
t oe 
Fic. 65.—Diagrammatic sagittal section of a “chain” Salpa. an, Anus; at, atrial 
aperture ; a¢.m, muscles of atrial aperture; atr.cav, atrial cavity ; br, branchial 
aperture; 67.m, muscles of branchial aperture ; 67.s, branchial sac; d./, dorsal 
lamina or “‘gill” ; d.t, dorsal tubercle ; end, endostyle ; kt, heart ; int, intestine ; 
l, sensory languet ; mus.bds, muscle-bands ; n.g, nerve-ganglion ; oc, eye-spot ; oe, 
oesophagus ; ov, ovary; p.p.b, peripharyngeal band; s.g/, neural gland; stom, 
stomach ; ¢,¢’, test ; tes, testis ; z, prebranchial zone. (After Herdman.) 
called the gill or branchia of Salpa), by means of which the 
cavity of the branchial sac is placed in free communication with 
the peribranchial cavity, are to be regarded as gigantic gill-slits 
formed by the suppression of the lateral walls and small stigmata 
of the branchial sac, The alimentary canal at the posterior end 
of the “gill” consists of oesophagus, stomach, and intestine, with 
a pair of lateral gastric glands or caeca. These viscera along 
with the reproductive organs, when present, make up the 
“nucleus” (Fig. 66, v). 
Alternation of Generations.—— Fig. 66 represents an 
ageregated or sexual Salpa, which was once a member of a chain, 
since it shows a testis and a developing embryo. The ova 
(always few in number, usually only one) appear at a very early 
period in the developing chain Sa/pa, while it is still a part of 
the gemmiparous stolon in the body of the solitary Salpa. This 
gave rise to the view put forward first by Brooks that the ovary 
