No. 1.] BUDDING IN GOODSIRIA AND PEROPHORA. 173 
as the intestine proper. By this time the pushing of the organ 
into the vesicle, as mentioned above, has advanced considerably 
(Fig. 32). With further growth the rectum becomes directed 
inward toward the branchial sac, as well as backward and dor- 
salward, so that, in the nearly adult state, transverse sections 
of the animal, which pass through the anal opening, already 
formed at a considerably earlier time, cut the rectum length- 
wise for some distance, at the same time that they pass trans- 
versely through the stomach (Fig. 6, az., vec., and s¢., Pl. XII). 
It will be observed in this figure how fully the whole digestive 
tract has now come to lie in the atrium and left peribranchial 
sac. The rectum reaches across the chamber, and comes in 
contact with the wall of the branchial sac, and actually forms 
a secondary attachment to it, so that a rectal mesentery is 
produced (Piss 34), wes.zec,, Fl XIV). In the, section this 
mesentery does not appear, but it does in sections a little far- 
ther back, none of which, however, would illustrate some other 
points as well as does this one; consequently, I have chosen 
this for the figure, and marked the position of the mesentery 
diagrammatically. The original mesentery (Figs. 33 and 34, mes. 
gas., Pl. XIV) is in the adult attached to the parietal portion of 
the atrial epithelium well out on its side, z.e. quite remote from 
the median ventral line, and extends across as a rather narrow 
band to the digestive tract in the region of the stomach and 
lacteal coecum (Fig. 34). The differentiation of the lacteal 
system into the coecum, the duct, and the ramifying portions, 
as we have seen them to exist in the adult animal, has been 
fully accomplished by the time the stage we are now consider- 
ing is reached. The same is true of the formation of the 
longitudinal folds of the stomach, and the peculiarly modified 
longitudinal band in the wall of the intestine. 
A secondary attachment of the rectum to the wall of the 
peribranchial sac is said by Hjort (93), p. 596, to take place 
also in Botryllus. 
