MUSEUM OF COMPARATIVE ZOÖLOGY. 57 
of this stage, in which the kamptoderm is long drawn out and easily 
overlooked in optical as well as actual sections, that led to the belief that 
polypide buds may arise independently of the body wall and only sec- 
ondarily become connected with it. 
At about this time the lumen of the alimentary tract begins to be 
separated from that of the atrium, Thus, in the series from which Fig- 
ure 81 was taken the more oralward lying sections show that the cavities 
of the lower and the upper parts of the bud, which at the anal end are 
broadly confluent, have here become separated by a constriction. A 
sagittal section of a somewhat later stage is shown in Figure 76, which 
is from Flustrella. Here we find the alimentary tract represented by a 
space in the lower part of the bud, broader at its anal than at its oral 
end and separated from the upper cavity — the common atrio-pharyngeal 
cavity, œ. + atr,— by a line of nuclei which represents the line of ap- 
proximation of the inner layers of the two sides of the bud. The bud is 
attached to the body wall at its marginal (anal) end, and is free from it 
oralwards. (Compare with Paludicella, Plate III. Fig. 24.) It seems 
to me highly probable from these and other series of sections that the 
alimentary tract is separated from the rest of the lumen of the bud, not 
by an approximation of the inner layers of the bud along the whole ex- 
tent of the future alimentary tract at once, but that the rectal part is 
first formed and constitutes a large cavity, at first broadly open to the 
atrium above, and that the gastric portion is formed somewhat later by 
a progressive enlargement of the lower cavity of the bud, which now 
becomes constricted off from the atrium and cesophagus above. This 
process is like that found in Paludicella (page 19), which forms a sort 
of transition to that of Phylactolemata, described by Braem (’90, pp. 
45, 46) and myself (90, p. 112). 
Prouho (90, p. 448, Fig. 6) shows that the rectum at first appears 
as a blind sac open to the atrium at its posterior end, although later 
this opening is greatly reduced. Hence in the Flustrella larva also the 
space from which the lumen of the future rectum is to arise is formed 
before that of the stomach, although this part of the alimentary tract 
is the last to be cut off from the atrium, Seeliger (’90, p. 585) says 
concerning the formation of the alimentary tract in Bugula : “ Der ganze 
Basaltheil des Polypids sich in der Mittelpartie durch zwei immer tiefer 
werdende Furchen von dem vorderen abschnürt, während er an zwei 
Stellen, einer oberen und einer unteren, mit ihm in Verbindung bleibt. 
Die obere Verbindung entspricht dem Anus, die untere dem Mund.” The 
author here seems to imply that the whole alimentary tract is formed at 
