FORM REGULATION IN CERIANTHUS ^STUARII. 



C. M. CHILD. 



During 1905-6 it was my privilege to enjoy for several months 

 the facilities afforded by the laboratory of the San Diego Marine 

 Biological Association at La Jolla, California. During this time 

 the work which forms the subject of the present paper, together 

 with other work to appear later was accomplished. I take this 

 opportunity of expressing my appreciation of the kindness of 

 Professor W. E. Ritter and the other members of the association 

 in granting me the privileges of the laboratory. 



In 1902-3 I made a study of the process of form-regulation in 

 Cerianthus solitarms at Naples, the results of which have already 

 appeared (Child, 'o3rt-'o5^). In order to test and compare the 

 results obtained with that species an extensive series of experi- 

 ments was performed with Cerianthus cestuarii (Torrey) which 

 occurs in abundance on the tide-flats of Mission Bay near La Jolla. 

 For the name of the species I am indebted to Professor H. B. 

 Torrey, as his work on the species has not yet appeared. 



As regards size and general appearance C. cestuarii does not 

 differ widely from C. solitarius. It is, however, more delicate in 

 structure, the body-wall and especially the muscular layer being 

 much thinner than in C. solitarius. In consequence of this 

 characteristic specimens which are all well distended with water 

 often appear more or less translucent. The length of the animal 

 varies greatly according to the degree of distension. Fig. i will 

 serve to give an idea of the usual shape. 



In general the results of my experiments with this species con- 

 firm in all essentials those obtained with C. solitarius, so that an 

 extended account of most of the experiments is unnecessary. But 

 the results of experiment differ in some respects in the two species, 

 and these differences, being due largely to the differences in the 

 character of the tissues, possess a certain interest. 



C. cBStuarii, like C. solitaritis, inhabits burrows whose walls con- 

 sist of slime, nematocysts and fine sand or mud* Like C. soli- 



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