606 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Tentacles simple, rather numerous and of three sizes arranged with 
some regularity. 
Dorsal tubercle C-shaped with incurved or inrolled horns. 
Dorsal lamina replaced by a row of numerous narrow tentacle-like 
languets. 
Branchial sac without folds, though a slight degree of minute fluting 
or plication is sometimes noticeable. Transverse vessels numerous, 
of two sizes placed alternately, the smaller ones crossing without 
interrupting the stigmata. Internal longitudinal vessels numerous 
but slender; they bear long curved papillae at the intersections with 
all of the transverse vessels. The papillae at the intersections with 
the smaller vessels are slightly smaller than the others. A membrane 
is borne on the concave side of each papilla. The number of stigmata 
intervening between adjacent internal longitudinal vessels is very 
variable in different individuals as well as in different parts of the sac 
of the same one, but averages greater in large than in small or immature 
specimens. It varies from four or six in the latter, to six, seven, or 
occasionally eight in the former. 
Stomach small and short with a small number of moderately dis- 
tinct longitudinal folds in its wall. Intestinal loop small, the rectum 
long. 
Ovary a pear-shaped mass, sometimes partly cleft into a few lobes, 
occupying the space in the loop of the intestine. At its narrow (dorsal) 
end it tapers off into the long, wide, tubular oviduct which accom- 
panies the rectum, lying along its left dorsal side. The oviduct often 
becomes greatly distended with eggs, these apparently remaining in 
it some time. The testis consists of a great number of small pyriform 
or more or less lobed glands connected by branching ducts, and rami- 
fies over more or less of the surface of the intestinal loop and stomach, 
its duct uniting to form a common sperm duct which lies along the 
dorsal edge of the oviduct. 
Ciena intestinalis (Linnaeus). 
PL 66, fig. 130; text-fig. 43. 
1767. Ascidia intestinalis Linnaeus, Syst. Nat., ed. 12, pt. 2, p. 1087, no. 3. 
1828. Ciona intestinalis Fleming, British Animals, p. 468. 
Said to be found in most parts of the world. In the Arctic regions 
replaced by an elongated pediceled variety (var. longissima Hartmeyer, 
