REPRODUCTION OF COSCINASTERIAS. 



117 



The ordinary, gametic reproduction of these starfishes takes 

 place in January-February. During summer months they are 

 quite abundant under stones along the shore, just under low- 

 water level. As winter approaches, they retreat for the most 



200 



160 

 120 

 80 

 40 



20 



2 5 4 5 G 7 8 9 10 II 



FIG. i. The ray- frequency polygon derived from counts of 487 Coscin- 

 asterias. The essential characteristics of this curve are identical with those of 

 a curve previously published (Crozier, '15). 



part to somewhat deeper water, it would appear. In January and 

 February, however, they crowd up to high-water mark, even on 

 exposed shores, within Great Sound at least, and in Harrington 

 Sound. 3 Often they are consequently left high above water level 



3 The question presents itself as to the possible role of phototropism in such 

 shoreward movements. C. tenuispina is photonegative toward strong light, 

 photopositive toward weak light ; it is probable that these animals become 

 photopositive toward slightly greater illuminations with lower temperatures. 

 This might play some part in determining movements into more illuminated 

 areas during the winter season; presumably gonadic secretions might also be 

 involved. Plessner ('13) came to the conclusion that the "eye-spots" of star- 

 fishes enable these creatures to respond to the direction of light; in C. tenui- 



