444 MOLLUSCS AND BRACHIOPODS. 



surface of the body, which is situated at the hinder end of the 

 shell and partly by the two leaf-like extensions of the body, which 

 are termed the dorsal and ventral mantles. These are, in fact, 

 folds in the body-wall, and into them the body cavity and certain 

 of its contents, such as the liver and generative glands, etc., extend. 



Microscopic examination of thin sections of the shell shows 

 that it consists of small prisms or spicules of calcareous substance, 

 whose long axis lies, roughly speaking, at right angles to the 

 surface of the shell. These spicules are held together by an 

 organic matrix, in which, however, no cellular elements can be 

 detected. In sections made through a decalcified shell the posi- 

 tion of the spicules which have been dissolved by the acid is 

 indicated by spaces, and the matrix remains as a network of 

 fibrils, which end on the outside in a thin cuticular layer of 

 organic matter. 



We trust we have said sufficient to interest our readers in these 

 very interesting classes, and to show how thoroughly the subject 

 has been treated by the authors. Our best thanks are due to 

 publishers for the use of the electros, and for permission to make 

 the above extracts. 



Solders for Glass. — Mr. Chas. Margot finds that an alloy 

 composed of 95 parts of tin and 5 of zinc melts at 200 degrees, 

 and becomes firmly adherent to glass, and moreover is unalterable 

 and possesses a beautiful metallic lustre ; and, further, that an 

 alloy composed of 90 parts of tin and 10 of aluminium melts at 

 390 degrees, becomes strongly soldered to glass, and is possessed 

 of a very stable brilliancy. With these two alloys it is possible to 

 solder glass as easily as it is to solder two pieces of metal. It is 

 possible to operate in two different manners. The two pieces of 

 glass to be soldered can either be heated in a furnace and their 

 surfaces be rubbed with a rod of the solder, when the alloy as it 

 flows can be evenly distributed with a tampon of paper or a strip 

 of aluminium, or an ordinary soldering iron can be used for melt- 

 ing the solder. In either case, it only remains to unite the two 

 pieces of glass and press them strongly against each other, and 

 allow them to cool slowly. — Set. American. 



