392 C. M. Child 
they are secondary heteromorphoses (Child ’ogb), since the 
elimination of the original polarity is the result of conditions 
which did not exist before isolation. But these cases are differ- 
ent from the usual form of axial heteromorphosis, forthey involve 
a change in the axes of symmetry as well as polarity. In the 
second series (Cases VI to IX, Figs. 21 to 29) where the groups 
of tentacles arise wholly on the oral side of the line of union there 
is no polar heteromorphosis like that inthe first series, but “radial 
heteromorphosis”’ is present. But the question as to whether a 
given case is or is not heteromorphosis seems to me of minor 
importance: we have simply to recognize the fact that in all of 
these cases the original polarity and symmetry are more or less 
completely obliterated and that polarity and symmetry of the new 
systems are more or less completely determined by local conditions 
in the material. In fact, as was noted above, comparison of the 
different cases shows that in some the old polarity and symmetry 
evidently play a part in determining the arrangement within the 
group (e. g., Figs. 8 and 10), while in other cases they do not 
appear at all (Fig. 29), unless the position of the tentacle groups 
on the oral side of the line of union is a consequence of the original 
polarity, which may or may not be the case. 
The restitutional phenomena in these rings are, in my opinion, 
cases of division of a system in consequence of decreased correla- 
tions between parts. Asexual reproduction can be induced ex- 
perimentally not only by inducing growth but by decreasing the 
correlations between parts. It is possible, for example, as lhave 
recently discovered, to induce fission experimentally in individ- 
uals of Planaria dorotocephala of any size above six or seven 
millimeters in length, even though they may have been decreasing 
in size from lack of food. The method usually employed is simply 
the removal of the head; frequently, especially in small individuals, 
it must be removed several times as it regenerates. “The removal 
of the old head decreases the correlation—in this case nerve co- 
ordination, at least in large part—between the anterior and pos- 
terior regions, and under these conditions the development of the 
new zooid in the posterior region is hastened, until sooner or later 
it becomes sufficiently independent to show independent motor re- 
