596 S. B. MITtlA. 



duced as a tough, solid substance, but is shed as a viscous, 

 finely bubbly liquid, Avhicli in the receptacle gradually gets 

 thicker and thicker in consistency, till it becomes a flexible 

 solid. It should be stated here that occasionally one notices 

 in a pretty freshly formed style in Anodon, an axial zone 

 that consists chiefly of particles of food material. Such a 

 zone is never found in fully formed styles in Anodon, and its 

 occasional presence in a freshly formed style in that animal 

 would seem to point to the imperfection of the method of 

 storing the ferment, and passing on the food material that 

 obtains in this species of the Lamellibranchia. It is inte- 

 resting to note in this connection, that such a zone is never 

 found in the style of a species of Pholas examined by me, in 

 which the style is lodged in a caecum, and not in the ali- 

 mentary canal itself. The style, let us add, in this species 

 of Pholas always possesses a central, liquid, finely bubbly 

 core (fig. 6), which never contains a particle of food material. 

 In fact, the main body of the style of this Pholas is always 

 free from a single particle of food material — an assertion that 

 cannot be made with regard to the style of Anodon. Under 

 these circumstances one is surely justified in thinking that 

 the complete freedom of Pholas' style from food particles is 

 due to a superior, more differentiated mechanism for storing 

 the ferment and passing the food material through the ali- 

 mentary canal. 



As is well known, the style is lodged in some species in 

 the alimentary canal itself (Anodon), in others (fig. 9) in a 

 diverticulum (caecum) of the canal, which starts from the 

 pyloric end of the stomach (Pholas). But the most curious 

 fact in this connection, that has never before been observed, 

 is that in Anodon the first portion of the intestine — the 

 portion that lodges the style — is divided into two longitudinal 

 compartments by two longitudinal ciliated ridges that project 

 into the lumen of the canal. A cross section of the canal at 

 this part, seen from behind, is represented diagrammatically 

 in the figure 7. One ridge is placed dorsally, the other 

 ventrally. The two compartments may, therefore, be called 



