BILATERAL TENDENCIES IN PYCNOPODIA HELIENTHOIDES. 233 



the bays at Bremerton, Pycnopodia had congregated in super- 

 abundance, offering a considerable inducement to perform experi- 

 ments on them there, rather than anywhere else on the Puget 

 Sound. And although much time was consumed in traveling 

 between Seattle and Bremerton, the abundance of specimens at 

 the latter place compensated fully for the time thus lost. Occa- 

 sionally a number of specimens were brought from Bremerton 

 and planted in Elliot Bay at West Seattle for the purpose of 

 studying them there, but when the salinity was found to fluctuate 

 more at the latter place than at the former, it was thought unwise 

 to study them in the new place as under normal conditions and 

 the efore, Bremerton was selected as the most logical place for 



collecting these data. 



ECOLOGY. 



DISTRIBUTION. 



Pycnopodia helienthoides is found along the Pacific Coast from 

 central California to southeastern Alaska. It inhabits the entire 

 Laminarian Zone, i. e., from low -water down to a depth of fifty 

 fathoms, or even beyond that. Very seldom is it caught above 

 low-water mark. When thus found, it is generally in pools 

 where the water remains fresh till the tide returns; when found 

 on piles under docks, after the tide has run out, it is because of 

 the fact that Pycnopodia does not readily move backward or 

 sidewise, but uses the side established as fore-end, always as 

 anterior end. In places where the bottom is sandy and void of 

 food and where nearby piles are covered with barnacles, Pycno- 

 podia may be found, at low-tide, above the water-line. As was 

 clearly demonstrated by some of the samples that were brought 

 to West Seattle and placed under an old dock there, at low-tide 

 a goodly number of them were found hanging on the dry piles. 

 These piles were covered with barnacles and the bottom below 

 was v?ry sandy and depleted of all kinds of food. The writer 

 has never found a duplication of this in other places, however. 

 It may be that the star in this particu'ar instance was excep- 

 tionally hungry and did not notice the decreased pressure as the 

 tide receded ; in places where food is readily obtained elsewhere, 

 Pycnopodia, as a rule, keeps below water. 



The Puget Sound region is well suited to Pycnopodia. The 



