148 
SIDNEY F. HAEM Ell. 
Fig. 34. — A similar specimen of much smaller size. Slide N. 
Fig. 35. — A very small regenerating fragment, the distal end of which 
is growing through the annular tube-septum (s.) which presumably 
indicates the previous occurrence of fission. Slide Q. 
Fig. 36. — A large specimen, of a kind frequently observed, in which 
the alimentary canal is thin and occupies only a small part of the 
body-cavity : a condition which is probably due to deficient nutrition. 
Regeneration of the distal end is taking place. Slide O. 
Fig. 37. — The two specimens here shown have probably been 
separated from one another by fission, as indicated by the septum 
(s.) and the lateral outgrowth of the tube on its proximal side. The 
lopliophore (Z.) of the proximal individual is in an early stage of 
development. Slide N. 
Fig. 38. — A very slender and presumably ill-nourished regenerating 
specimen. Slide N. 
Fig. 39. — The significance of the condition here shown has not been 
ascertained. The entire muscular region has been invaginated, forming 
an introvert opening to the exterior at or. The introvert contains 
a regenerating distal end, in which the new muscular region (muse.) 
and lopliophore ( l .) can be distinguished. By the formation of the 
introvert the alimentary canal has been thrown into a loop, the portion 
of which belonging to the descending limb (pr.) is seen to the right 
of the introvert. The ascending limb of the alimentary canal probably 
has a similar course, but it was not observed in this specimen. The 
outgrowth of the proximal end of the body in a direction at right 
angles to the axis of the original tube probably indicates a lateral 
extension of the proximal end of the tube in order to provide room 
for the elongation of the corresponding region of the body, the growth 
of which, in this direction, would otherwise be prevented by the 
septum s. Slide N. 
Fig. 40.— Lateral view of the distal end of a mature specimen, 
showing the epistome (ep.) inside the group of retracted tentacles. 
Slide M. 
Fig. 41. — Another stage of the condition shown in fig. 39. The 
introvert contains a bundle of fully developed tentacles. This may be 
either an earlier stage than fig. 39, in which case the original lophophore 
has been completely retracted into the introvert, and was destined 
to be thrown off later ; or a later stage, in which the new lophophore 
has been completely regenerated. In this specimen there is evidence 
that the ascending limb of the alimentary canal, as well as its 
descending limb, forms a loop passing up one side (left in the figure)- 
of the proximal end of the introvert. Slide M. 
