74 THURLOW C. NELSON 



system of Anodonta cellensis. According to him, three gastric 

 nerves arise from the cerebrovisceral commissures of each side, 

 just posterior to the cerebral ganglia. These send branches 

 to the oesophagus, but principally supply the wall of the 

 stomach. As a result of the intercrossing of many nerve fibers 

 there is formed here a 'solar plexus' from which fibers extend 

 downwards to the wall of the intestine and style sac. This 

 latter region is, therefore, in close nervous connection with 

 the anterior centers of control. 



Histology of the style sac and accompanying organs 



By far the most extensive and careful part of all former work 

 on the crystalline style has been concerned with the structure 

 of the cells of this region. When one sees the long ciliated cells, 

 with their large distinct nuclei, besides the several types of se- 

 creting cells, it does not seem strange that so many investigators, 

 setting out to study the style in all its relations, should have 

 been sidetracked by the beautiful histological material before 

 them. Inasmuch as the present problem lies rather in the 

 realm of physiology than that of histology, I shall consider here 

 only such details of cell structure as are necessary to understand 

 the mechanism for the secretion and movement of the style. 

 For a more complete account of the histology of the alimentary 

 canal of lamellibranchs the reader is referred to the works of 

 Sabatier (77), Barrois ('-SQ), List ('02), and Gutheil ('11). An 

 extensive treatise on the structure of ciliated cells, and the 

 mechanism of ciliary action with special reference to the typhlo- 

 sole of Anodonta, will be found in the work of Erhard ('10). 



Figure 2 is a transverse section of the style sac and intestine 

 of Lampsilis anodontoides, showing the typhlosoles incom- 

 pletely separating the two tubes. The typhlosoles are highly 

 vascular, and are composed of loose connective tissue lying be- 

 tween the lacunae or haemal spaces. Very few nuclei occur here. 

 The epithelium of this region is composed of a single layer of 

 long ciliated cells resting on a basal membrane. The cytoplasm 

 is usually filled with many refractive granules and stains rather 



