CRYSTALLINE STYLE OF LAMELLIBRANCHS 83 



style (fig. 14). This spiral structure was recognized by Barrois 

 ('89) and illustrated in several figures. 



In the stomach minute sand grains, tests of diatoms, and simi- 

 lar waste matter, entangled in mucus, are beaten by the cilia 

 into compact masses. Passing into the intestine, this waste 

 material is carried along in the deepest part of the intestinal 

 groove. During periods of active feeding some food particles, 

 diatoms, unicellular algae, etc., escape from the stomach and 

 pass down the intestine with the sand and dirt. As this es- 

 caped food matter is less compact it comes to lie closer to the 

 typhlosoles, and, if the particles be very small, they may be caught 

 by the cilia on the edges of these structures and carried across 

 to the style. Larger particles, such as the larger diatoms, pass 

 downward until they reach the region of the diverticulum at the 

 end of the style sac. Here they are caught by the cilia and 

 carried into the stream of mucus at this point, while the waste 

 materials pass on through the intestine. Thus it happens that 

 this twisted mucous thread in the style sac so often contains food 

 particles in a very fresh condition. 



It has been seen (p. 75) that in the typhlosoles there are two 

 types of secreting cells, long goblet cells, and mucous glands. 

 As the spiral mucous thread is passed anteriorly from the diver- 

 ticulum, in contact with the-edges of the typhlosoles on the 

 right side of the style sac, the secretions from these unicellular 

 glands are carried by ciliary action across the faces of the typhlo- 

 soles and applied to it. By the action of the thousands of power- 

 ful cilia of the style sac these globules of secretion are beaten 

 into a homogeneous mass around the mucous thread, which 

 forms the core. 



As this structure moves anteriorly, turning on its axis, suc- 

 cessive layers of secretion are added to it, until as it nears the 

 stomach, further additions cease and the fully formed crystalline 

 style passes out of the style sac into the stomach. 



The styles of different individuals o' the same species exhibit 

 the most diverse modifications, depending on the physiological 

 state of the animal prior to examination. A specimen which 

 has been starved for some time and then put into water contain- 



