OIRCULATORY APPARATUS OF THE NEMERTEA. 47 
against the inner surface of the inner longitudinal muscular 
coat, and stretches no farther back than the dorsal vessel in 
the proboscidian sheath. The canals are very thin, with a very 
small lumen and relatively thick walls. Anteriorly the system 
does not reach the mouth. Also in Lineus sanguineus I 
found many more than one pair of excretory ducts. 
I have only traced it in two specimens, an old one (X) and a 
young one (Y). All the excretory ducts lay above the nerve 
trunks in the sections here enumerated : 
X. ¥: 
Closure of the Mouth-slit 210. Closure of the Mouth-slit 75. 
Left side. Right side. Left side. Right side. 
228 5 : 240 99 : Nothing. 
? - : 309 121 : : 121 
341 ‘ ; 325 Nothing : 125 
358 : : 353 133 é ‘ 134 
Bee |... ; 373 ? 136 ; Nothing. 
Nothing. : 377 ? 143 : Nothing. 
405 : 3 4.04 147 : ‘ 146 
419 : - Ald 153 : Nothing. 
437 : : 437 The dorsal vessel leaves the pro- 
447 ‘ : 446 boscidian sheath in 155. 
476 : : 472 
The dorsal vessel leaves the pro- 
boscidian sheath in 479. 
Also this observation points to the increase of the number 
of excretory ducts in proportion to the growth and age of the 
animal. 
T could not see ciliain the canals. In Lineus sanguineus 
—at least in the two specimens examined by me—the excretory 
ducts were not so close to the lateral nerves. If we trace a 
horizontal line through the centrum of the transverse section 
of the body the nerve stems lie just beneath this line, and the 
excretory ducts of X lay at an angle of 45°, that of Y at an 
angle of 5°10° inclined against the horizontal line. 
Though X was older than Y the excretory ducts of X were 
limited by smaller cells and less visible, that of Y by larger 
cells, contiguous, as in Valencinia, and immediately visible, 
