192 LO IOI BY se [VoL. XII. 
Series of figures similar to these, representing both younger 
and older stages, might be multiplied indefinitely were it neces- 
sary; but the main facts, vzz., those concerning the relation 
of the zooid to the stolonic septum, are so clear that no further 
illustration is required. And this is the more so because 
Lefevre (95) fully confirms my results in this particular. In 
Fig. 65 I have shown a single instance from many that 
might be given of the same relations in a bud of Pevophora 
Lister. 
The connection between the septum and the peribranchial 
sac becomes entirely lost at a stage only a little later than that 
represented in the series 57-64. Lefevre states that the 
severance does not occur until a somewhat later time in 
P. viridis, This difference in the two species may be corre- 
lated with the fact that the zooids of the P. annectens colony 
are closely bound together by the test, and hence depend less 
on the stolon for maintaining their colonial character than do 
those of P. vzvidis. It is certain that in some cases, at least in 
P. annectens, the buds become wholly severed from the stolon, 
the ectodermal as well as the endodermal connection being cut 
away. I have shown an instance of this in Fig. 66. This is 
the section of a complete series in which the stolon, s¢o., with 
its septum approaches most nearly to the wall of the zooid; yet 
there is a distinct absence of connection between them. I am 
unable to say with what frequency this complete separation takes 
place, but so far as I have been able to determine it appears 
that it is rather exceptional. Certain it is that the stolons of 
a colony are always in communication with many of the zooids 
because the blood is always in motion in the living colonies, 
and there is, of course, no other propelling power than the 
hearts of the zooids. 
I have stated that the connection is always to the left pert- 
branchial sac. This has been true for every undoubted instance 
observed, but it does not seem in the least improbable that 
exceptions might be found were one to examine a sufficiently 
large number of cases; though that it is well-nigh the invaria- 
ble rule is certain from the large number of instances of its 
occurrence that have been observed. 
