THE VOYAGE OF H.M.S. CHALLENGER, 
a,, anal aperture ; at., atrial cavity opening into the common cloacal cavity ; Br., branchial aperture ; hr.s., the branchial 
sac; cl., common cloacal aperture; ec., the ectoderm bounding the vascular appendage; en, endostyle ; gl.n, neural 
gland ; h., heart ; i, intestine ; i.gl., hepatic gland on the intestine ; I, languet ; ni, mantle ; n.g., nerve ganglion ; 
(e, CRSophagu-s ; ov., ovary ; 2>-P, peripharyngeal band ; r, rectum ; si, stomach ; t, the test or investing mass ; tn, one 
of the tentacles; t.v., a testicular vesicle; v.ap., the vascular appendage; v.d., vas deferens. The limits of the 
thorax, abdomen, and post-abdomen are shown by the dotted lines extending outwards to the left, one at the lower 
end of the endostyle and another below the intestinal loop. 
