152 



PROTOPLASM 



dichromate ; a drop of strong silver nitrate was put in the center. 

 As the silver nitrate diffused into the gel and met the dichromate, 



Fig. 91. — A, Crystals of basic mercuric chloride in a silica gel produced by 

 allowing mercuric chloride to diffuse into a gel of basic reaction, on a plate; B, the 

 same in a tube; C, rhythmically produced disks of silver dichromate (K2Cr207 + 

 AgNOs, with a little potassium citrate in the gel); D, like C, but showing scat- 

 tered granules as the disks become irregular; E, ammonium chloride disks pro- 

 duced by ammonium hydroxide diffusing into a gelatin gel containing magne- 

 sium chloride; F, rhythmic banding of lead iodide in a gel in imitation of agate. 



silver chromate was precipitated. There is no evident reason 

 why the precipitated silver chromate should not be evenly- 

 distributed and give to the gelatin plate a fine granular appear- 



