BILATERAL TENDENCIES IN PYCNOPODIA HELIENTHOIDES. 247 



above to the fact that Pycnopodia was found in large numbers on 

 a certain side of a bay, during spring, while it was totally absent 

 from these grounds later on, during the summer. As a matter 

 of fact, during the spring of 1915, on the area ACBD (Fig. 3) 

 more than one hundred specimens were counted, while in July 

 of the same year not a single specimen was seen on the same area. 

 The change in habitat was perhaps due to the intense sunlight, 

 as during the cool and rainy summer of 1916, a large number was 

 seen on the same area until constant sunny weather ensued. 

 As demonstrated above, this is an indication of positive helio- 

 tropism. The habitat of Pycnopodia ranges over the entire belt 

 of the laminarian Benthos; it lives as a rule in deeper water during 

 the warm and light part of the year, and in shallower water 

 during the spawning season and during the darker and colder 

 part of the year. 



FEEDING. 



Kinds of Food. 



The feeding habit of Pycnopodia is striking and very interesting 

 indeed. It lives on such types of mollusks as clams and gaster- 

 pods; on crustaceans, such as crabs and barnacles; on other 

 echinoderms, such as common starfish and sea-urchins; on pori- 



fera, and on algae. 



Methods of Feeding. 



The methods of feeding are by engulfing and sucking. Large 

 rocks up to a pound in weight have been found in the stomach. 

 These were engulfed when sucking on barnacles, because mark- 

 ings of barnacles could be seen on the rocks. The large horse 

 clam (Schizoth&rus nauttalli] cannot be engulfed on account of 

 its enormous size. But when Pycnopodia encounters Schizothce- 

 rus, it rolls itself around the latter and proceeds to digest it. 

 On one occasion the writer found the star in the act of consuming 

 one of these large horse clams. The extraordinary large syphon 

 was forced into the mouth of the starfish while the everted 

 stomach was folded around the syphon. The whole star had in 

 fact, rolled itself around the clam, endeavoring to pull it open. 

 This pulling on the part of the star had, however, no effect on the 

 clam, for, although the latter might have relaxed to the continu- 

 ous pull of the sucker-feet, it was of no avail because the folds 



