VAN NAME: SIMPLE ASCIDIANS. 499 
on the anterior part but with small triangular teeth rather widely 
spaced on the posterior part. 
Branchial sac provided with well marked but rather low folds, 
seven on each side, each bearing three internal longitudinal vessels 
along its summit, except the most dorsal fold, which is rudimentary, 
and bears but one or two. The most ventral fold may also be reduced 
and bear but one or two vessels. There are none of these vessels 
in the intervals between the folds. In most parts of the sac there 
are two orders of transverse vessels placed alternately, those of the 
first or largest order numbering five on each side of the body. In 
addition there are very slender tubules which cross the stigmata and 
pass to the summits of the infundibula described below\ There is 
on each fold one large infundibulum between each pair of transverse 
vessels of the first order, except on the fold next to the endostyle where 
there are two, each transverse vessel of the second order here becoming 
of the size of, and assuming the character of one of the first order 
while one of the slender tubules mentioned above, situated midway 
in each interval assumes the size and character of a vessel of the second 
order. Each of the above described infundibula divides in its upper 
portion into an anterior and a posterior apex, separated by a transverse 
vessel of the second order. 
Stigmata mostly elongated, and wide in proportion to the vessels 
separating them. They are straight or nearly so only in the case of a 
few situated between folds, becoming curved on the infundibula and 
spiral on the summits of the latter. Sometimes the spirals on the two 
summits of an infundibulum curve in the same way, in other cases in 
opposite ways. 
Stomach with few irregular longitudinal folds in its cardiac portion, 
the pyloric portion being smooth-walled and tapering off gradually 
into the intestine. Over a considerable portion of its surface, however, 
especially on the posterior side, there is a thick glandular mass of 
small rounded or short fold-like caeca opening into the stomach and 
constituting an hepatic organ of greater bulk than is usually present 
in this genus. The intestinal loop has a course which is mainly 
horizontal, the reflected end being but little bent up dorsally. 
Kidney sausage-shaped, rather wide for its length and situated, as 
in related species, against the right posterior part of the body wall. 
It usually contains a few small concretions. 
In the specimens dissected (all collected during the summer months) 
