THE CRYSTALLINE STYLE OF LAMELLIBKANCHIA. 591 



The Crystalline Style of Lamellibranchia. 



By 



S. B. ]?Iitra, 



Of Calcutta, late of University' College, London. 



With Plate 42. 



Four hypotheses have been framed with regard to what 

 the crystalline style of the Lamellibranchia is and does : (1) 

 Gegenbaur thought it was a secretion from the enteric 

 epithelium ('Elements of Comparative Anatomy/ English 

 translation, p. 359). (2) Balfour suggested that it was to be 

 considered as a rudiment of the radular sac of the Glossophora 

 (see Professor Lankester's article on " HoUusca/' in the 

 ' Encyclopaedia Brita.nnica/ ninth edition, p. 685). (3) 

 Glaus regarded it as an excretion of the enteric epithelium. 

 (4) Sedgwick thinks it is to be regarded as a " reserve of 

 nutriment " (' Student's Text-book of Zoology,' vol. i, p. 335). 

 We may say at the outset that of all the hypotheses 

 Gegenbaur's was the nearest to the truth, for it is in reality 

 a secretion, a digestive ferm'eut whose function it is to 

 digest starch, i. e. to convert starch into a reducible sugar. 



The crystalline style cannot be regarded as a rudimentary 

 structure representing the radular sac of the Glossophora, 

 for the following reasons :^ 



(1) Its comparative size is not like that of a rudimentary 

 structure. It is fully three fourths as long as is the animal 



' A structure apparently identical in nature with the crystalline style of 

 Lamellibranchs co-exists in some Gastropoda with the radula. If the 

 identity of the Gastropod's and Lamellibranch's crystalline styles be admitted 

 there can be no question of relationsliij) to the radula. — E. K. L. 



