FACTORS OF FORM REGULATION IN HARENACTIS 
ALTENUALAS 
III REGULATION IN “RINGS” 
BY 
C. M. CHILD 
Witu Tuirty-one Ficures 
I EXPERIMENTAL DATA 
1 The Formation and Structure of Rings 
Certain methods of formation of the peculiar structures, which 
for lack of a better name I have termed “rings.” were briefly 
described in first paper of this series (Child ogb), as illustrations 
of the remarkable results which the wound-reaction may bring 
about under certain conditions. 
The basis of the ring is a rather short cylindrical piece cut from 
any region of the body distal to the attenuated portion. Pieces 
between any two of the consecutive levels of section indicated 
in Fig. 1, or even somewhat shorter pieces than these would serve 
under certain conditions for the formation of rings. 
The ring is formed _ by the union of the oral with the aboral cut 
surface of the body-wall, and such union almost never occurs except 
perhaps in very short pieces, unless longitudinal wounds exist on 
the mesenteries, whose contraction approximates the oral and 
aboral cut surfaces of the piece. These longitudinal wounds may 
be produced in various ways; for example, in a piece such as ad, 
Fig. I, we may simply remove the cesophagus by cutting the mesen- 
teries which hold it in place, or in subcesophageal pieces such as 
cd or de, Fig. 1, we may remove the longitudinal muscles before 
the piece closes. These operations are not difficult except for the 
fact that the very strong contraction of the body-wall under the 
continued stimulation often results in tears or other injuries which 
