FACTORS OF FORM REGULATION IN HARENACTIS 
ATTENUATA 
II ABORAL RESTITUTION, HETEROMORPHOSIS AND POLARITY 
BY 
C. M. CHILD 
Witn Twetve Ficures 
Changes in polarity, including both the so-called reversal of 
polarity and other changes occur very readily in Harenactis, prob- 
ably more readily than in any other actinian which has thus far 
been made the subject of experiment. The present paper is 
chiefly concerned with the description and discussion of these 
changes. 
I THE REGIONAL FACTOR IN ABORAL RESTITUTION 
I Aboral Restitution in the Hsophageal Region 
The method of closure of aboral cut surfaces within the cesopha- 
geal region is the same as that of oral surfaces in the same region 
(Child, ’ogb), i. e., the contraction of the parts injured by the opera- 
tion approximates the cut margins of body-wall and cesophagus 
and union occurs. The consequence of this method of union is 
that the cesophagus opens aborally to the exterior instead of into 
the enteron, and no connection exists between the enteron and 
the exterior. In this respect Harenactis resembles Cerianthus 
and all other species of actinians which I have examined. 
The further history of such cesophageal pieces depends to a 
considerable extent upon their length; short pieces from the oral 
part of the cesophageal region—e. g., distal to the line ain Fig. 1— 
usually do not live for more than a week or two and the regulatory 
changes at the aboral end rarely proceed beyond the closure of 
Tur JouRNAL oF ExPERIMENTAL ZOOLOGY, VOL. VII, NO. I 
