DIRECTION OF LOCOMOTION OF THE STARFISH 



25 



b, c, d, and e, as denominated by Jennings. In case two adja- 

 cent rays took an equal part in the lead, 'one-half time' was ac- 

 credited to each.i" Except for Luidia, which is a seven-rayed form, 

 Preyer's ('86-7, p. 218) results are brought together in table 5. 



Preyer states that the brittle-stars Ophiomyxa and Ophio- 

 derma showed just as little preference for any particular ray; 

 but a careful inspection of table 5 will show that this conclu- 

 sion regarding the starfishes was scarcely justified bj^ the results 

 presented. In fact these results show a striking similarity to 



TABLE 5 



Summary of Preyer's results on the direction of locomotion 



those presented in the earlier part of this paper. Not only is 

 this apparent in the individual records for each species (note 

 the small number of times c was used as compared with the 

 ray opposite it), but is especially noticeable when comparison 

 is made of the totals (cf. table 5 with table 2, p. 10). In the 

 case of Preyer's results, however, the plane of bilaterality would 

 not pass through the radius e; but the plane which would have 

 most nearly an equal number of records on each side, would 

 cut through the interradius ea and ray c. Such a plane has 

 eighty-one records to the left, seventy-eight to the right. So 

 if we thus lump together then the four species of starfishes with 



'"This accords with the treatment of the data in the jiresent i)aper (cf. table 

 1, and fig. 4). 



