REPRODUCTION OF COSCINASTERIAS. 



125 



senting such great variations, it was possible to obtain a fairly 

 definite idea of the relative values of ray-length and madrepore- 

 position as determiners of the " physiological anterior " ; for 

 Coscinasterias does show definite tendencies in the orentation of 

 its body with respect to creeping. Since the organization of the 

 body of this starfish is somewhat irregular, the observations can- 

 not be summarized in terms of morphologically defined rays (I 

 did not note the position of the anal opening in these cases ; cf . 

 Gemmill, '14). I must therefore give several instances in detail 

 (Table V.). 



TABLE V. 



SHOWING THE NUMBER OF TIMES EACH RAY OF THE STARFISHES ILLUSTRATED 

 IN FIGS. 4 AND 5 WAS USED AS " DIRECTOR." 



In the creeping of Coscinasterias, which is rather slow (at 24, 

 about 1215 cms. per min.), several points are similar to ones 

 emphasized by Cole in Asterias, notably the tendency to exhibit a 

 definite region as " physiological anterior," with, however, clear 

 evidence of the "rotation" of this anterior. 4 A good instance 

 of such rotation is the following : 



Coscinasterias No. i, September 9, 1915. Creeping under ver- 

 tical light, the region in advance shifted slowly, in this order (cf. 

 Fig. 5) : i, i, ii, ii-i, ii, ii, iii, iii-iv, v-iv, the animal being undis- 

 turbed from the outside. 



Such " rotation of the impulse " was observed to be either 

 clock- or anticlockwise. Ordinarily rotation of this sort was not 



4 Agersborg ('18), in describing the righting movements of the "twenty- 

 rayed " Pycnopodia helianthoides, has spoken of " bilateral tendencies " in the 

 activities of this starfish. But the condition of his tests are not well specified, 



nor is there any indication given of a relation between the " bilaterality " and 







structural conditions in Pycnopodia. 



