NATURE OF EXCRETORY PROCESSES IN MARINE POLYZOA. 151 
In Bugula avicularia the “ brown bodies” are usually 
situated in a similar position, at the distal end of the zocecium, 
and the leucocytes are in most cases aggregated around them. 
There was not much reason to suppose that the pigment taken 
up by the leucocytes passed into the “ brown bodies.” 
In this species, parts of the wall of the alimentary canal 
took up indigo-carmine. In one case observed, the feeces cir- 
culating in the intestine of one of these polypides contained 
bright blue particles, indicating that some of the pigment 
taken up by the walls of the cavity may be excreted with the 
feeces. Most of the indigo-carmine, however, does not escape 
in this way; and the “brown body,” when formed, is very 
obviously blue-green in colour, owing to the admixture of the 
indigo-carmine with the natural pigments of the stomach. 
At 261 hours after the commencement of the experiment it 
was noticed that many of the old zoccia had developed new 
srowing-points at their tips; and some of these already pos- 
sessed polypides. Blue-coloured leucocytes had in these cases 
passed in an apparently unaltered state from the old zocecia 
into the young growing-points. No obvious alteration of the 
indigo-carmine contained in these leucocytes took place 
during the whole of this experiment, which lasted about 350 
hours. 
CARMINATE OF AMMONIA. 
B. neritina.—The pigment taken up by the walls of the 
alimentary canals is left in the ‘‘ brown bodies” formed by 
their degeneration. The part of the “brown body” formed 
from the tip of the cecum is at first very brilliantly coloured 
by the pigment. By the 286th hour the colonies contained 
numerous compact “ brown bodies,” which were most dis- 
tinctly carmine-coloured. Many of the polypides whose 
development had commenced since the beginning of the 
experiment were nearly mature. At the time of the last 
observation made (478th hour) no change of importance had 
taken place. The zocecia were left with ‘‘ brown bodies” con- 
taining carmine, and probably destined to remain permanently 
