VAN NAME: SIMPLE ASCIDIANS. 517 
smaller ones are simply pinnate with a few branches, or if very small, 
are entirely unbranched. The tips of the branchlets are not swollen. 
Dorsal tubercle with an oval orifice. 
Dorsal lamina rather narrow, plain-edged. 
Branchial sac with six approximately equal folds on each side. 
These folds do not actually represent much plication of the wall of the 
sac, but the group of internal longitudinal vessels which are borne on 
them (and, except for two or three very slender irregular and rudi- 
mentary ones, not elsewhere) gives them the appearance of having 
considerable height, for these vessels are raised up on tall supports 
considerably above the level of the summit of the fold on which they 
are borne. Transverse vessels of two orders placed alternately, 
numbering ten in all. 
The stigmata are rather few, broad and short, and between the 
folds are longitudinal or only slightly oblique in direction. As the 
summit of a fold is approached they become more oblique until they 
lie at an angle of about 45 degrees to the transverse vessels, becoming 
at the same time smaller and shorter, and assuming an arrangement 
in spirals whose centers lie at the summit of the folds midway between 
the transverse vessels. The spiral is, however, an angular one, made 
up of straight stigmata successively shorter as the center is approached, 
and each placed at right angles to the preceding one of the series; 
the stigmata do not in this species exhibit the tendency to curve that 
is usual in the genus Caesira. These spirals are raised into low py- 
ramidal infundibula having a square base. 
The esophagus is unusually long and slender, the stomach wall is 
dark brown in color and is expanded into a number of capacious 
sac-like caeca of irregular form and arrangement, but the plications 
forming these caeca tend to a longitudinal rather than a transverse 
arrangement. The intestinal loop has its branches open for some 
distance from the reflected end ; they then lie nearly parallel and close 
together. The whole loop forms a curve widely open dorsally. 
Margin of anus sinuate. 
No kidney and no left gonad were discovered, but the writer is not 
prepared to say that they were wanting. 
The gonad on the right side contains an elongated tapering tubular 
ovary with a few eggs in various stages of development. Its smaller 
end, where the orifice is situated, is directed dorsally toward the base 
of the atrial siphon. The male part of the organ consists of only five 
