306 



Moreover may be remarked that the bundles are separated by 

 muscular fibres placed the one upon the other , so as to form a wall. 

 These diaphragms being distinct on the convex edge of the 

 jaw disappear near the basis of the jaw, the bundie of the ex- 

 cretory ducts forming here a compact mass. In my figures 3 

 and 4 the muscular fibres , which fbrm the diaphragm are repre- 

 sented as t. s. and it may be remarked , that they extend from 

 the epithelium of one side of the jaw to that of the other side. 

 In order to study the minute details of the jaw , it is impor- 

 tant to cut the jaw in the right direction and therefore I have 

 isolated the jaw and imbedded in parafine. Geuerally the paraf- 

 ine was transparent enough to determine the position of the jaw. 

 In order to examine the lacunae between the denticules I pro- 

 ceeded in the following way. 



The jaws were carefully isolated , treated with alcohol and oil 

 of cloves and mounted in Canada-balsam , the sharp edge facing 

 upwards. 



By using a high magnifying power I was able to study the 

 jaw from above and to distiuguish very exactly the openings be- 

 tween two neighbourhing denticules and the cuticular edges. 



In studying a sectiou of the jaw stained with Haematoxyline 

 with a lesser power , the bright blue colour of the glandducts con- 

 trast distinctly with the dark blue colour of the muscular fibres, 

 but the ultimate structure of the ducts cannot be made out. This 

 becomes distinct in using a high magnifying power (oii-immer- 

 sion Vjg) and we see what I have tried to represent in my fi- 

 gures 3 and 4. 



The glandducts have a smootli thin wall , the outlines are 

 very sharp The contents of the glandducts is formed by nu- 

 merous small granules , quite of the same structure and appea- 

 rance as the granules of the glaudcells tliemselves and which 

 staiu very well with Haematoxyline. 



The glandducts go for the greater part towards the sharp 

 convex edge of the jaw, tlieir course however is not straight 

 but a little undulatinsf. 



