No. 3.] BUDDING IN PEROPHORA. 389 
oesophagus, stomach, and intestine takes place very early, and 
is apparent at a stage considerably younger than that shown in 
Pl. XXIX, Fig. 4. The course and development of the tube 
are sufficiently illustrated by Figs. 4 and 5. 
As the. bud grows and increases in length, the digestive 
tract enlarges enormously, the U becomes opened more and 
more, and the intestine describes a wide curve which lies well 
forward against the outer wall of the left peribranchial sac 
(Fig. 5). With the anterior extension of the digestive tract 
and the posterior prolongation of the left peribranchial sac, the 
whole tract, which lies entirely on the left side of the bud, 
comes eventually to be closely enveloped by the outer wall of 
the peribranchial cavity. 
The “ pyloric gland”’ or ‘‘organe réfringent ” of Giard arises 
as a tubular diverticulum from the lower anterior face of the 
enlarged portion of the digestive tract which will become the 
stomach. Before reaching the intestine the tube bifurcates, 
and each branch in its turn gives off two others, which also 
divide, the whole system of dichotomously branching tubules 
finally forming a lace work surrounding the whole intestine. 
The development of this problematical organ is already well 
advanced at the stage shown in Pl. XXIX, Fig. 5 (o.~7.). This 
figure, together with Pl. XXXII, Fig. 30, which shows a por- 
tion of the stomach wall (s¢.w.), leaves no doubt that the tube 
is directly derived from the digestive tract. This origin was 
maintained by Della Valle (3), but denied by Roule (25), who 
stated that the “ organe réfringent”’ is not a part of the digest- 
ive tract, but communicates with the heart, and therefore 
belongs to the vascular system, an opinion already held by 
Kuppfer (16). 
Della Valle’s view is also supported by Pizon (22), whose 
description of the development of the organ in Botryllus agrees 
minutely with my observations on Perophora. 
The terminal branches of the system of tubules which 
ramify over the surface of the intestine end in little enlarge- 
ments or ampullae, the walls of which are very thin, and lie 
closely pressed against the intestinal wall. The cells of the 
duct are cylindrical, and gradually pass over into the flat cells 
