12 BRUCE—ON THE ACTIVITY OF 
Experiment VII. 
A drop of a dilute solution of carbonate of ammonia 
was placed on the sessile glands, which after twenty-four 
hours’ became darkened, owing to the salt having been 
absorbed. On looking at the glands several days after- 
wards they had quite lost their black colour, showing that 
they had not been killed. 
These experiments show that the sessile glands of Bybles 
gigantea possess the power of digestion. This power, however, 
seems to be limited, since if the piece of albumen is too large, 
it is not all digested. This might, however, be due to the 
white of egg absorbing so much of the moisture into itself, that 
the glands are injured and unable to continue resecreting.* The 
secretion from the sessile glands differs from that of the stalked 
glands in being acid to litmus. The sessile glands do not secrete 
spontaneously, a fact which is shown since particles of glass did 
not bring forth any secretion, neither did a perfectly dry piece of 
albumen. — If, however, the albumen is moist and contains a little 
soluble nitrogenous matter, this causes the glands to pour forth 
immediately their secretion, which is acid, and is able to digest 
animal substances. The soluble nitrogenous matter which is 
required to cause the glands to secrete probably enters the gland 
by osmosis through the cell-wall, since if the albumen is fresh, the 
secretion is poured forth quickly, and the cube of albumen is 
rapidly dissolved. If the cube is not quite so fresh, it will have 
dried up to a certain extent, and there will not be so much 
soluble nitrogenous matter, so that the osmosis will not take 
place quite so quickly, the glands will take longer to be stimu- 
lated, and will, in consequence, not pour out their secretion so 
quickly, and this is exactly what I found to be the case. If, on 
the other hand, the albumen is completely dried there will be no 
nitrogenous material present in solution, the glands will not be 
stimulated, and no secretion will be poured out. 
After the secretion has digested the animal remains, the dis- 
solved matter is absorbed by the glands, as is shown by their 
* Compare the effect described later of placing too large pieces on the 
stalked glands. 
