STUDIES ON BIOLOGY OF FRESHWATER MUSSELS. 223 



4. THE PHYSIOLOGY OF THE CRYSTALLINE STYLE. 



Everyone, myself included, who has dealt with the crystalline 

 style during the past decade, has made apology for adding to the 

 bulky list of the things not certainly known concerning that 

 organ. 



(a) Recent Studies. 



The most thoroughgoing and satisfactory account of the crys- 

 talline style is that of Nelson ('18). He has assembled and or- 

 ganized the literature on the subject to the minutest detail, has 

 very effectualy eliminated most of the groundless speculations, 

 and has sifted out the truth contained in the rest. Nelson's work 

 on the morphology is of a sort which virtually closes that sub- 

 ject. All future studies of the crystalline style may well make 

 Nelson's work the point of departure. 2 There is no occasion to 

 review the literature here or to describe either the style itself or 

 the associated portions of the alimentary tract. I shall be content 

 to record the physiological data which have accumulated during 

 the intermittent observations made over a period of some six 

 years. 



Most of the writers, with the exception of Mitra ('01), and 

 Nelson (l.c.~), have taken a viewpoint which has been fatally 

 erroneous, it seems to me. Despite all the divergent speculations 

 which observers have permitted themselves to make (a point well 

 reviewed by Nelson), they have really been looking for one 

 explanation the most plausible function that this organ might 

 be supposed to perform. Few have granted the probability that 

 two or more uses of the style might exist concurrently. 



- The preceding sentence, when written, was prophetic. For just as this 

 paper is about ready for the press, Edmondson's timely account of the crystal- 

 line style in Mya arenaria has appeared ('20). Like Nelson, he has devoted 

 considerable study to the morphology, but has centered his attention upon the 

 renewal of the style. It is gratifying to find others interested in the physio- 

 logical study of the style, for, aside from its chemistry, most work has been 

 done from the viewpoint of structure. 



This author's account of Mya arenaria shows the style to have diverged 

 very far, indeed, from its homologue in the Unionidze. It lies in a distinct 

 caecum. Operative methods instead of starvation were necessary to remove 

 it. It is a very solid structure, nearly insoluble, and nearly devoid of albu- 

 minoids. Its regeneration in Mya precedes rather than follows resumption of 

 feeding. Seventy-four days were required for its reformation in Mya, while 

 one day more or less suffices in the Unionidx. 



