FACTORS OF FORM REGULATION IN HARENACTIS 



ATTENUATA 



I WOUND REACTION AND RESTITUTION IN GENERAL AND THE 

 REGIONAL FACTORS IN ORAL RESTITUTION 



BY 



C. M. CHILD 



(With Twenty-four Figures) 



The present paper is concerned with a part of the data obtained 

 by the writer on form regulation in Harenactis attenuata (Torrey, 

 '02) during a stay of several months in the autumn and winter of 

 1905-06 at the laboratory of the San Diego Marine Biological 

 Association at La Jolla, California. This actinian occurs in 

 great numbers in the fine sand or mud of the tide-flats of False 

 Bay and San Diego Bay and is extremely hardy in the laboratory. 

 Its usual form and habit and the regulatory changes which occur 

 under certain changed environmental conditions have been de- 

 scribed elsewhere (Child, '09) and only one or two points require 

 mention here. Figs, i and 2 are diagrammatic outlines about 

 two-fifths of the natural size, of the shape of individuals in the 

 extended condition, Fig. i being a condition approaching maxi- 

 mum extension and distension in large individuals and Fig. 2 a 

 size and shape nearer the average. Extension and distension to 

 the degree indicated in these figures occur only when the animal 

 is in its burrow in the sand. When removed from its burrow and 

 kept without sand during several months it gradually undergoes 

 regulation into a shape resembling that of the "sessile" actinians 

 (Child, '09). Under the usual conditions of life the circular mus- 

 cles of the body-wall are well developed and the mesenteries bear 

 powerful longitudinal retractor muscles inserted distally on the 

 walls of the oesophagus, whose contraction invaginates the disc 

 and tentacles (Fig. 3). The mesenteries, the mesenterial fila- 

 ments and the longitudinal muscles, particularly the latter, occupy 



The Journal of Experimental Zoology, vol. vi, no. 4. 



