SEA-FISHERIES LABORATORY. ots 
nearly horizontal. At its upper extremity the coiling 
becomes rather irregular, and the tube passes into the 
succeeding coiled portion of the intestine near the axis of 
the latter. The crystalline style passes the opening of the 
spiral intestine, and its narrowed end is lodged in the 
short caecum already referred to. The anterior fold in 
the straight intestine continues on into the spiral portion, 
and passes into a thick pad, nearly filling up the lumen 
of the latter (Ty., fig. 18, Pl. III.). This pad or typhlosole 
is formed by the same tissue which fills up the space in 
the anterior and posterior folds which divide the straight 
eut into right and left divisions. Owing to the presence 
of this typhlosole the spiral gut appears externally as a 
round tube, although in section the lumen is contracted 
and crescentric in form ; the tissue filling the typhlosole is 
continuous with a narrow layer surrounding the gut and 
with the general connective tissue of -the viscero-pedal 
mass. 
After making about six turns the typhlosole disappears, 
and the intestinal tube passes into a loose coil of four or 
five turns, which may be described as the coiled portion 
of the intestine (Al.c.5, figs. 3 and 11), and which lies 
anterior to the spiral gut. The average diameter of this 
coil is from 0°6 tol cm. Its most anterior turn joins the 
spiral intestine ; its most posterior one passes off into the 
rectum, which passes to the right side of the straight 
intestine, and runs up along the posterior part of the 
viscero-pedal mass (Al.c.6, figs. 3 and 11) to near the 
dorsal portion of the latter, where it pierces the muscular 
body-wall and enters the pericardium. After passing 
through the ventricle of the heart, the rectum runs along 
in the dorsal body-wall over the posterior adductor, and 
terminates in the anus (An., fig. 3). 
The histological character of the epithelium of the intes- 
