NOTES ON SOME PROBLEMS OF ADAPTATION. 



2. ON THE TEMPORAL RELATIONS OF ASEXUAL PROPAGATION 

 AND GAMETIC REPRODUCTION IN COSCINASTERIAS TENUI- 

 SPINA: WITH A NOTE ON THE DIRECTION OF PROGRESSION 

 AND ON THE SIGNIFICANCE OF THE MADREPORES. 1 



W. J. CROZIER, 

 HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



I. 



Some time ago I gathered evidence showing that in the common 

 Bermuda starfish, Cosdnasterias tenuispina (Lamk.), there is 

 unmistakable evidence of asexual multiplication through spon- 

 taneous division of the body into two parts (Crozier, '15). The 

 modal number of rays in the adults of this species is J 2 ; the parts 

 resulting from self division commonly constitute either 3 or 4 

 rays; each of these parts most usually produces 4 new rays. I 

 may give here some additional data obtained in subsequent years, 

 leading to the same conclusion (Fig. i, Table I.). 



TABLE I. 



THE RELATION BETWEEN THE NUMBER OF LONG AND THE NUMBER OF SHORT 



RAYS IN 237 COSCINASTERIAS, OF WHICH EACH INDIVIDUAL HAD 



Two DISTINCT GROUPS OF RAYS. 



The table shows that as a rule 4 short rays are found in association with 

 either 3 or 4 long rays. 



LONG RAYS 



1 Contributions from the Bermuda Biological Station for Research. No. 121. 



2 It is entirely probable that here, as in Solaster (Gemmill, '12) and in Lep- 

 tasterias (Osterud, '18,), the fundamental ray number is 5, to which at an 

 early age a sixth and, later, a seventh ray are normally added (cf. Crozier, '15). 



116 



