278 CHARLES HOWARD EDMONDSON 



According to Gutheil ('11), the gastric shield is built up by a 

 hardening of the material secreted by the epithelium on which 

 it rests. Nelson ('18) states that it is probably in the nature of 

 chondrin. In Mya arenaria the structure is very resistant, slight 

 dissolution of its thickest region occurring during a period of 

 about thirty days after the removal of the crystalline style. 



This peculiar structure, without doubt, serves as a protection 

 to the epithelium of the wall of the stomach which it covers, and 

 at the same time it assists in the wearing away of the end of the 

 crystalline style which, in its rotation, presses against the concave 

 surface of the thickened portion of the shield (fig. 17). 



6. DETAILS OF THE EXPERIMENTS 



In presenting the details of the various experiments carried on 

 for the determination of the reformation of the crystalline style, 

 following its extraction, in Mya arenaria, it is my purpose to con- 

 sider the series of experiments in the order of the progressive de- 

 velopment of the crystalline style rather than the chronological 

 order in which the experiments were conducted. 



Experiment 1. September 19, 1918 



Six medium-sized clams, with crystalline styles removed by trans- 

 verse sectioning of the style sacs about 10 mm. from the distal extremi- 

 ties, were replanted under normal conditions. The experiment was one 

 of short duration, continuing for six days, with the object in view of 

 determining the exact character and position of the crystalline style 

 in its initial stage. 



Result, September 25, 1918. After six days all of the clams operated 

 upon were found to be alive and in good condition. The severed ends 

 of the style sac were healed in each individual, and in one or two speci- 



Fig. 19 A section of the left wall of the stomach of Mya arenaria with the 

 gastric shield closely applied to the inner surface of the epithelium. Bm, base- 

 ment membrane; Gs, gastric shield. X 84. 



Fig. 20 The regenerating crystalline style four days after extraction, the 

 clams being out of water and without food but subjected to low temperature. X 

 2i 



Fig. 21 The crystalline style after a growth of six days under normal condi- 

 tions. X 2J. 



Fig. 22 The same as the preceding figure. X 2. 



Fig. 23 A regenerating crystalline style thirteen days after extraction. X 2. 



