370 C. M. Child 
underwent reduction to mere stumps and death occurred a few 
days later. ; 
II DISCUSSION AND ANALYSIS OF DATA 
t The Nature of the Tentacle Groups A 
The question as to whether the groups of tentacles which appear 
on the rings represent more or less close approximations to com- 
plete oral ends has already been touched upon in the description 
of case [X. It seems to me that the general form of these groups, 
the frequency of a radially symmetrical arrangement of tentacles 
and mesenteries and the formation of a short column below the 
tentacles in most cases all indicate that these structures are in 
reality new oral ends, more or less different from the normal be- 
cause the conditions under which they arise are more or less widely 
different from the normal. If this conclusion is correct the for- 
mation of these structures involves the establishment of new polar- 
ities about the circumference of the ring, and if we can judge from 
the appearance of the eroups of tentacles, such polarities are very 
evidently established. 
The number of tentacles is indefinite, at least up to ten (Fig. 12a) 
or twelve (Fig. 10). Groups with even numbers of tentacles are 
much more frequent than groups with odd numbers, even in cases 
where the tentacles are not equally distributed on the two sides of 
the line of union (Fig. 12, a@and b). This fact is significant, since 
it suggests at once that the mesenteries in these groups are usually 
paired as in the normal animal. Moreover, most of the groups 
with odd numbers of tentacles are the result of the failure of ten- 
tacles to appear on the aboral side of the line of union opposite 
those on the oral side (Fig. 12, groups c and d; Fig. 15, groups 6, 
c and d). Probably these cases are due simply to early cessation 
of growth in these rings; if conditions favorable to growth con- 
tinued to exist for a longer time there is little doubt that these 
cases would become symmetrical with an even number of tentacles 
liketheothers. Inthe first series of these rings, in which the tentacles 
of each group arise from the two sides of the line of union, only 
one group with an odd number of tentacles has been observed, viz: 
