CRYSTALLINE STYLE OF LAMELLIBRANCHS. 93 



Nelson, and Edmondson, and that in the light of the findings of 

 these and of other workers a more critical series of experiments is 

 needed to determine the relative importance of food and of oxygen 

 in determining style formation. Berkeley concludes that the 

 presence or absence of the style depends upon the presence or 

 absence of oxygen, and he makes the astonishing assumption that 

 food plays no part in the building up of this structure, on the 

 ground that oatmeal added to the water caused no regeneration of 

 the style. No examinations were made to determine whether the 

 animals were eating the oatmeal, nor were any tests made using 

 the natural plankton food of the molluscs. 



Taking the results of Martin and Berkeley together, however, I 

 believe that Allen and I were mistaken in laying undue emphasis 

 upon the role of food in stimulating style secretion. Although 

 the presence of food in the stomach may play a part in the 

 mechanism of style formation, Edmondson's finding that no food 

 was taken by Mya until after the head of the regenerating style 

 protruded into the stomach; Martin's results in obtaining style 

 regeneration in aerated water devoid of all net and nanno- 

 plankton; and Berkeley's conclusion that no style forms under 

 anaerobic conditions, all point to the probability that secretion of 

 the crystalline style may be a direct response to siphoning, 

 regardless of whether the incoming water contains food organisms 

 or not. 1 



The chief criticism centers about the following conclusions of 

 Berkeley; first, his assumption that since the style disappears 

 when the bivalve is kept under anaerobic conditions it therefore 

 represents a reserve of oxygen. As well might one conclude that 

 all secretions contain reserve oxygen since secretion is diminished 

 during decreased activity of the organism. Second, no corre- 

 lation was shown between the size and persistence of the crystal- 

 line style on the one hand and the degree of aeration of the 

 environment on the other. As bearing upon the first of these 

 assumptions Gray, '23, showed that for ciliary movement the 

 degree of mechanical activity exactly parallels the relative amount 

 of oxygen absorbed. Since the formation and movement of the 



1 Orton, '24, I.e., pg. 55, observes that sound O. edulis will reform a stj'le in the 

 absence of food, but from the text it is not clear that all nannoplankton was removed 

 from the water. 



