No.1.] BUDDING [N GOODSIRIA AND PEROPHORA. I9QI 
adult zooid. The rotation is not so great in P. annectens, as 
may be determined by considering Fig.67. The heart Anlage 
is certainly somewhat higher than it will be at a later time, as its 
position with reference to the stolonic septum, in this section 
shows. I have seen no specimens in which the Az/age was at a 
higher point, and I think that this particular individual furnishes 
evidence that no appreciable rotation could have taken place in 
the earlier stages of development. This evidence consists in 
the uniform thickness of the wall of the vesicle in all its parts, 
thus indicating that there has been no considerable inequality 
of growth, to which Lefevre probably rightly attributes the 
rotation; and to the fact that at this time the connection of 
the septum to the vesicle is not yet thrust off to one side as it 
later comes to be (Fig. 70) when the rotation is complete. It 
is undoubtedly to this rotation that the attachment of the 
septum to the left peribranchial sac is due. 
The greater or less extent of the rotation in various species 
probably has no particular significance beyond the general 
significance that attaches to variations in development. 
From this early stage we may now pass to the examination 
of one much farther advanced. Such a one is shown by the 
series of Figs. 57-64, all from the same bud. The sections 
pass from the anterior toward the posterior of the animal, and 
are seen on their anterior surfaces, thus causing an apparent 
reversal of right and left. In Fig. 57 the peribranchial sacs 
are entirely distinct from the branchial sacs, and this is the 
condition for a considerably greater portion of the anterior 
part of the bud. Fig. 58 shows the point at which the three 
cavities become confluent. From here the ventral partitioning 
folds, v.f, rapidly fall away; compare Fig. 59, seven sections 
farther back. A few sections farther back (Fig. 60) they have 
almost wholly disappeared, and the three cavities have become 
practically one. This section, with those going before it, shows 
clearly, however, that the bay, /.f0.s.,1s the posterior tip of the 
left peribranchial sac. But this is the point at which attach- 
ment to the stolonic septum, c/’z., occurs. It will be seen that 
the ventral side of what will later be the branchial sac is far 
below this, it being marked by the already forming endostyle, end. 
