CKYSTALLINE STYLE OF LAMELLIBRANCHS 57 



The gastric shield is represented by the ' Cristallgriffin/ of 

 Bojanus ('19), 'Knorpelstiel,' of Hazay ('81), 'dreizackige Pfeil 

 of Jordan ('13), 'fleche tricuspide,' or 'sagitta tricuspis,' of Poli 

 (1791), and the 'stomachal cuticle' in Pelseneer's volume on the 

 Mollusca in Lankester's Treatise. 



Historical 



A complete chronological review of the literature dealing with 

 the crystalline style would be beyond the limits of the present 

 paper. A comprehensive digest of all former investigations and 

 theories is, however, necessary, I shall, therefore, sum up 

 most of these data, not chronologically, but group the various 

 authors according as their conclusions favor one theory or 

 another. 



The following account is based chiefly upon the historical 

 summaries found in the works of Barrois ('89, '90) and List ('02). 

 Wherever discrepancies occur between the accounts as given here 

 and for all of the important works, reference has been made to 

 the original articles. 



Anton de Heide (1686), in his monograph of the common 

 mussel, describes the 'stylus cristallinus.' He refers to the 

 work of Willis on the oyster, six years previous, in which he 

 described a structure analogous with the 'spinali medullae' of 

 the vertebrates. From the text it is probable that Willis re- 

 ferred not to the style, but to the typhlosole separating the 

 style sac and true intestine. We are therefore justified in rec- 

 ognizing de Heide as the discoverer of the crystalline style. 

 Its function was ignored by this investigator who, however, 

 hazarded the guess that it might be an alimentary ferment or 

 perform some role in the act of generation. 



Lister (1696), in his anatomy of bivalve molluscs, pictures the 

 stylus of Pectunclus vulgaris and Mytilus marinus (edulis), but 

 gives no appreciation of the structure or usage o ' them. 



Swammerdam (1737) refers to the presence of the style in 

 Mytulus belgicus, evidently a fresh-water species. 



Lesser (1744) reviews the literature to date, but adds no con- 

 tributions of his own. 



