82 THURLOW C. NELSON 



List ('02, p. 274) fed finely ground color particles to Mytilus, 

 and observed that these were built up into the structure of the 

 style. He claims frequently to have seen the style in the proc- 

 ess of formation, in which the typhlosoles furnished the secre- 

 tion in large quantities. He concludes (p. 277), ''dass der 

 Krystallistiel im Darme entsteht, und dass hauptsachlichdie 

 Secrete der seitlichen Epithelwiilste (typholsoles) an seinem 

 Aufbau betheiligt sind. ' ' 



Gutheil ('11), as a result of an extensive study of the ali- 

 mentary tract of Anodonta, concluded that a ciliated epithelium 

 might also be absorptive and secretory as well. He found cells in 

 the ' Kristallstieldarm' which were loaded with clear vacuoles 

 lying above the nucleus. These structures he is certain were 

 neither artifacts nor products of degeneration, but material 

 destined to become the style. His conclusions are, therefore, in 

 entire accord with those of List. 



My own studies of the secretion and formation of the crystal- 

 line style were made on the living material and with stained 

 sections. It is evident from these observations that List was 

 right in placing the origin of the style in the typhlosoles. We 

 have already seen (p. 67) that in forms where the intestine and 

 style sac are incompletely separated by the typhlosoles, a short 

 diverticulum occurs at the end of the style sac. This communi- 

 cates freely with the intestinal groove down which pass the 

 waste materials from the stomach. 



In animals taken during the height of feeding activity, and 

 quickly dissected, a thin thread of large mucus globules may be 

 found issuing from the diverticulum. At the same time there 

 may be seen a string of whitish, ropy mucus, which is secreted 

 by the walls of the intestine for a short distance beyond the di- 

 verticulum. The two streams unite at the mouth of the diver- 

 ticulum and pass anteriorly into the style sac. 



The cilia here, as we have already seen, beat so as to put 

 into rotation any matter in contact with them. As a result, the 

 round or flattened stream of mucus is twisted on itself as it 

 starts on its way toward the stomach, thus giving rise to the 

 spiral arrangement typical of the smaller, posterior end of the 



