CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY 

 OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT 

 HARVARD COLLEGE, NO. 256. 



ON THE NUMBER OF RAYS IN ASTERIAS 

 TENUISPINA LAMK. AT BERMUDA 1 



BY W. J. CROZIER 

 Harvard University 



I. It was suggested by Clark (1901) that the average 

 number of rays borne by Asterias tenuispina was different 

 for separate localities in Bermuda, He examined forty 

 specimens of this species— eleven from Coney Island and 

 twenty-nine from Harrington Sound; in the first set the 

 average number of rays was 5.91 (I find the mode to be 6), 

 in the second set 6.93 (with a mode of 7). If this condi- 

 tion really obtains, it would be an exceedingly interesting 

 matter to determine the factors responsible for this sort 

 of difference. I have therefore examined a number of 

 Asterias (312 in all) from several localities in the Bermu- 

 das, namely: Agar's Island, Spanish Point, Hawkins 

 Island, Ely's Harbor, Hungry Bay, Harrington Sound 

 and Coney Island; the first four are situated on the 

 periphery of Great Sound, the others at widely removed 

 points on the north and south shores. For the identifica- 

 tion of these places, references may be made to the maps 

 published by Mark (1905). 



These observations were made at the Bermuda Biolog- 

 ical Station, mostly during the summer of 1914. 



II. The first lot of starfishes was collected in the imme- 

 diate vicinity of Agar's Island in 1913. The number of 

 rays varied from 2 to 9; the frequency distribution is 

 given in Fig. 1. The modal number of rays is clearly 7. 

 In 1914 a collection of Asterias from this place gave the 

 ray frequency distribution shown in Fig. 2, where the 

 modal number of rays is again 7. Collections, during 

 1914, at the other stations named gave the following ray 

 frequency counts : 



i Contributions from the Bermuda Biological Station for Kesearch, No. 35. 



28 



