38 D. KEILIN 
secretion (1889) a fairly large literature on mucin glands has 
accumulated, and several good methods now exist which 
enable us to detect the smallest amount of mucin in very fine 
ductules. Jor a eritical account of these methods, the reader 
is referred to the papers of Hoyer (1890 and 1908) and Michaelis 
(1903). 
The methods of stammg which I have used in connexion with 
this study are of two kinds : 
(a) A purely mucin stain: Mucihaematem of P. Mayer 
(1896). 
(b) Metachromatic stains: Thionin and Toluidin blue. 
(a) Mucin stain: Anterior portions of earthworms are 
fixed for twenty-four hours in Bouin’s Picro-formol or in 
a modified solution of Bouin’s Picro-sublimate formol (Corro- 
sive sublimate, saturated sol. 20 ¢.c., Picric acid, saturated sol. 
20 ¢.c., Formol, 20 ¢.c., Acetic acid, glac. 5 ¢.c.). After fixation 
they are well washed in Alcohol (70 per cent.) and embedded by 
the ordinary method. The sections (4-6 in thickness), having 
been freed from paraffin, are stained from two to five minutes in 
a 10 per cent. solution of Mucihaematein. They are then either 
mounted without any supplementary staining, or stained with 
the Magenta-red and Picro-Indigo-carmine. I have obtamed 
sood results by staining the sections with Iron Haematoxylin 
(twelve hours in Iron alum and twelve hours in 1 per cent. 
solution of Haematoxylin) and counterstaiming for five minutes 
in Mucihaematein, and for a few seconds in Orange G. 
(b) Metachromati¢ stain. Slightly modified methods 
of Hoyer (1890, 1903) and Hari (1901) give very good re- 
sults. Portions of earthworms are fixed either in 5 per cent. 
solution of corrosive sublimate, or, with much better results, 
in the above-mentioned Picro-sublimate formol, from two to 
eight hours. ‘The sections, freed from paraffin, are passed 
through the geries of alcohols into the distilled water and then 
for ten minutes into 5 per cent. solution of corrosive sublimate. 
They are then washed rapidly in strong alcohol and distilled 
water and stained in an aqueous solution 0-1 per cent. of Thionim 
(Lauth’s violet), or Toluidin-blue. In about one to two minutes 
