134 
SIDNEY F. HARMKR. 
septum is also lobed, and this region shows indications of 
regeneration, particularly in the commencing differentiation 
of an oesophageal portion of the descending limb of the 
alimentary canal. It appears to be practically certain that 
this specimen represents a stage not long after the occurrence 
•of transverse fission. 
In PI. 9, fig. 37, there are also two individuals in what 
may be considered one original tube. The individual on the 
proximal side of the septum already shows a recognisable 
lophophore and oesophagus, but it is constituting a new distal 
end to its tube by growing out laterally from the original 
tube. 
(c) Method by which the Tube of the Proximal 
Segment is completed. 
The specimen last described furnishes the evidence 
required, and the explanation it suggests is fully confirmed 
by a number of other cases which have been noticed. In 
most of the specimens referred to, a tube makes a sudden 
bend outwards, immediately on the proximal side of a trans- 
verse septum ; and tliis outwardly bent portion contains the 
distal end of an individual. This is represented, for instance, 
in PI. 8, fig. 9, and PI. 9, fig. 34 ; and the natural interpretation 
of the conditions shown is that the portion of the tube contain- 
ing the proximal end of the individual in question is part of 
an original tube, from the rest of which it is separated by the 
transverse septum ; and that at the formation of this septum 
the proximal part of the tube, being cut off from the exterior 
by the septum, has grown out laterally so as to form a new 
opening for itself. It may be noted that the formation of 
these laterally growing tubes makes it almost impossible to 
accept the view of de Selys-Longchamps, alluded to on p. 12, 
that the tube is secreted only by the ampullar end of the 
animal. 
The system of empty tubes represented in PI. 8, fig. 15, 
may be taken as distinct evidence, in the light of the facts 
