No. 577] 



NUMBER OF BAYS IN AS TE BIAS 



31 



ossicle is shown by the fact that even in preserved ma- 

 terial the rays part very easily in that region. 



The relative abundance of cases in which there are evi- 

 dent two groups of rays of different length indicates that, 

 as in Linckia (Clark, 1913), autotomous division is a 

 normal method of asexual reproduction. 



IV. The numerical relations of the old rays to the re- 

 generating ones, and the topographical arrangement of 

 the latter, yield evidence relative to certain questions in 

 the physiology of regeneration. 



(a) It is to be observed that the regeneration in ques- 

 tion has taken place apart from experimental control; 

 therefore information as to the number of rays usually 

 present just before Asterias undergoes self-division must 

 be deduced from the data at hand. The modal-ray fre- 

 quency for specimens with rays of very nearly equal 

 length is 7 (Fig. 10), but it is a question whether this ap- 

 pearance of equality in ray length may not be due to a 



