The Shell of the Cuttle Fish. 1 75 



salicine or asparagin ; but greater care is required for the cuttle 

 shell than for theni, and even an experienced microscopist may 

 not immediately hit upon the right way. Perhaps no polar- 

 iscope slide is better adapted to assist the artist-designer in 

 devising patterns for shawls, carpets, and other ornamental 

 goods, and the effect may be varied not only by the methods 

 we have indicated, but also by the degree of fineness of the 

 powder employed, and by determining, as we shall presently 

 explain, the proportion which the amorphous dull golden par- 

 ticles bear to the most brilliant and crystalline portions of the 

 display. But to make this intelligible we must, at all risks of 

 offending very learned readers, say a few words on the structure 

 of the cuttle shell, and the mode of examining it. 



The first step is to cut a little block of the soft brittle sub- 

 stance of which what may be called the inside of the shell is 

 composed. If such a block is viewed in vertical section as an 

 opaque object, it will appear to consist of a great many tiers of 

 columns of a* white glittering semi-transparent substance, about 

 one-fortieth of an inch high, and between each tier of the tiny 

 pillars a flooring of somewhat similar material will be seen to 

 run. Thus the first idea of construction would be that of 

 dozens of floors supported by millions of columns, and many 

 sections may be made and viewed in various directions without 

 the real principle of the fabric being found out. A horizontal 

 view, when one floor has been cut away, may perhaps disclose 

 the secret ; but the apparent columns are so brittle, that enough 

 of them may not remain after the knife has passed through 

 them to show the true form. By beginning at the back of the 

 shell the chance of success is greater. First, a rough brittle 

 layer of carbonate of lime is removed, then comes a transparent 

 glassy-looking substance, and behind this the pillars begin, 

 and a portion of the flooring may be taken away without 

 materially disturbing the order in which they stood. If this 

 does not readily yield a good horizontal section, a cube of the 

 shell may be saturated with the colourless varnish used in 

 photography, and when this is dry the brittle part will be 

 strengthened sufficiently to bear rougher usage without harm. 

 However it be accomplished, if the horizontal slide is well 

 made, it at once becomes obvious that the columnar appearance 

 was an optical mistake, and that instead of the floors resting' 

 upon thousands of separate pillars, they are supported by the 

 sheet of carbonate of lime, corrugated just as a sheet of papei 

 would be by folding it alternately backwards and forwards 

 across a square-edged ruler. The chemical nature of the several 

 parts may be readily ascertained by acetic acid. If a few 

 minute fragments from different portions are placed in a drop of 

 dilute acid, covered up with thin glass, and placed under the 



