I ALIMENTARY CANAL 13 
connected at intervals by chitinous “synapticula” (Fig. 5, s), 
which traverse one or the other of the halves of the gill-slt. In 
Dolichoglossus, where no synapticula occur, the tongue-bars may 
be turned inside out by slight pressure, and then project to the 
exterior through the gill-pores. 
The subdivision of the branchial region of the alimentary 
canal into two parts, as shown in Fig. 4, is characteristic of 
Glossobalanus and its allies. In Dolichoglossus and Glandiceps 
there is no such constriction, the region occupied by the gill-slits 
being merely the dorsal half of a tube with a simple circular. 
section. Schizocardium (Fig. 
6) agrees with Amphioxus 
in the fact that the gill-slits 
occupy nearly the whole of 
the wall of the pharynx; 
the only parts not perfor- 
ated by gill-slits being the 
small dorsal and ventral 
portions. 
In Ptychodera (Fig. 4), 
the gill-sacs are practically 
absent. The U-shaped shts 
of the pharyngeal wall thus 
Fic. 6.—Schizocardium brasiliense ; transverse 
open directly to the exterior,! section through the branchial region, show- 
] ii i an ing the great extent of the branchial part 
and can be seen Irom e (6) of the pharynx ; the oesophageal part 
outside. In species which (9) is reduced to a mere groove; g, gill- 
pore ; g.s, gill-sac ; 7, reproductive organ ; 
have this arrangement, the 5, synapticula (cf. Fig. 5); ¢, tongue-bar. 
genital wings are greatly The muscles of the body-wall are not indi- 
cated: in other respects the figure corre- 
developed, so as to arch over sponds with Fig. 4, except for the absence 
the back of the branchial of genital wings in this region of the body. 
; ; : (After Spengel.) 
region. The gill-shts thus 
open into a kind of “atrium,” resembling that of Amphioxus 
in its relation to the gill-slits, and in having the generative 
organs on its outer side, but differing from it in being dorsal to 
the pharynx. 
At a certain distance behind the branchial region, the 
alimentary canal in Balanoglossus and Schizocardium is produced 
into a series of outgrowths, into which food does not pass. 
These “liver-sacs” give rise to corresponding folds (Fig. 1, A, h 
5 fo) oD ? 
1 Spengel, Monogr. pp. 179, 187 ; Willey, Zool. Res. iii. p. 236. 
