, CEYSTALLINE STYLE OF LAMELLIBRANCHS 89 



Such a condition is present in the oyster larva for the first 

 week or ten days. As the free-swimming stage reaches its 

 close, and the oyster larva attaches itself to some foundation, 

 the mucous roll of the stomach is represented by a short rod 

 extending backwards into the lumen of the intestine. Mean- 

 while the intestine becomes constricted lengthwise to form two 

 tubes. In an oyster 4 mm. in diameter the organs are well dif- 

 ferentiated and a distinct style is present. In a 9-mm. indi- 

 vidual this differentiation is apparently complete. The style is 

 comparatively short and thick and is as clear as crystal. It 

 shows the same twisted inner core as is found in the adult. 

 The gastric shield is likewise well developed at this stage. In a 

 9-mm. oyster it measures approximately 0.7 x 0.5 mm. The 

 style of a 7-mm. oyster measures about 1.2 mm. long and 0.3 

 mm. in diameter at its widest extent. 



At this time the young oyster has all of the organs for food- 

 getting of the adult and eats the same food. We may suppose, 

 therefore, that the style now serves it in the same manner as it 

 does the adult. 



3. NATURE 



Description of the style 



The length of the style is described by Mitra ('01) as fully 

 three-fourths that of the animal. Gutheil ('11) gives a more 

 conservative estimate, the style from an Anodonta 13 to 14 cm., 

 measuring from 6 to 7.5 cm. Biederman ('10,-' 11) gives the 

 length of the style of an adult Anodonta as 7 to 8 cm. My 

 own observations agree closely with those of the last two in- 

 vestigators, though the length of the style varies greatly with 

 the species and the feeding activity of the animal. 



Figure 14 shows the appearance of the style as taken from 

 its sac, with a mass of food material attached to the anterior 

 end. This figure gives an optical section through a style con- 

 taining a thick core of food material, showing the spiral arrange- 

 ment of this inner core and the layers of hyaline substance which 

 have been secreted upon it. 



