Form Regulation in Harenactis attenuata 393 
action, i. €., to attach itself to the substratum independently of the 
anterior region, and thenseparationoccurs. ‘These experiments will 
beconsidered more fully clsewhere, but it seems to me worth while 
to point out that the tentacle groups on the rings are a kind of 
asexual multiplication, i. e., a division of the system which is 
determined primarily by changes in the correlations of parts, 
which decrease or obliterate the original polarity and symmetry. 
Asexual reproduction is very frequently due, as I hope to show 
elsewhere, to a decrease in correlation or to escape of certain 
parts from correlation. In my consideration of the formation of 
aboral hydranths in pieces of Tubularia (Child ’07) I touched 
upon this point and showed that the various phenomena could 
readily be accounted for on this basis. In the case of Harenactis 
asexual reproduction does not occur or occurs very rarely in nature, 
but under the peculiar conditions existing in the rings a certain 
kind of asexual reproduction does take place. While it does not 
produce individuals capable of long-continued existence, this 
feature is undoubtedly incidental, and it seems at least highly prob- 
able that the formation of a number of more or less independent 
systems, the tentacle groups, in the rings is physiologically very 
similar to many cases of asexual reproduction which occur in 
nature. Moreover, as I suggested in connection with Tubularia 
(Child, ’07a, b,) all cases of axial heteromorphosis, whether pri- 
mary or secondary, undoubtedly belong in the same category. 
The principal points of the paper may be summarized as fol- 
lows: 
1 Rings are formed from cylindrical pieces of the body of 
Harenactis by the union of the oral with the aboral end about the 
whole circumference. Their formation can be induced experi- 
mentally by removing a larger or smaller part of the mesenterial 
organs from the piece, and in the cesophageal region by removing 
the cesophagus. In general, the shorter a piece the more likely 
it is to form a ring in closing: when the length of the piece is less 
than the diameter a ring is usually formed or closure does not occur 
at all. 
2 After closure the parts of the ring commonly undergo a 
revolution about a circular axis, so that the line of union between 
