207 
[Fewkes. 
Are we dealing here with phenomena of a similar character or have 
we organs with two or three different functions ? Are these dis- 
charges when thej^ occur simply the throwing off of excretions, or 
do they also serve for protection of the Medusa from its foes? 
It seems not improbable that the physiological function of certain 
of the tasters, which are known as cystons in Forskalia is that of 
excretion. This power of throwing off excretions may also serve 
for protection. Yet it must be borne in mind that all the Calyco- 
phoridse, the Pneumatophoridse and Hippopodise have no cystons 
or similar excretory organs, nor has the function of excretion yet 
been referred in them to any special organs. Is it possible that the 
discharge of colored matter from the pigment cells of the bract of 
Agalma is also a method of excretion, and is it the same as that of 
the cystons of Forskalia? It seems to me improbable that we have 
to deal with excretions only, in this case, although we may have 
an instance of a novel' means of protection, which is in part ac- 
complished by the discharge of the excretion in Forskalia. Upon 
this theory, however, we need much more light which can best come 
from more observation. 
It is legitimate to conclude that the discharge of a highly col- 
ored fluid by the scales of Agalma is in part a means of protec- 
tion for the medusa, and it would seem natural to connect it with 
the function of excretion, but we know so little about the character 
of the excretions, and the manner in which they are produced in 
Medusse, that at present we can hardly definitely ascribe the spec- 
ial function to these glands. Possibly similar glands are found in 
other Physophores, and the excretion has not been recognized from 
the fact that it is not so highly colored as in Agalma clausi and 
Forskalia. The discharge of this fluid from a living animal, if it 
take place without rupture of the wall of the scale, would imply 
special excretory openings somewhere on the bract, and one is 
tempted to search for such openings, if they exist, on the distal tip 
of the scale, when they would be homologous to the excretory open- 
ings known to exist on the bell margin of certain Hydromedusse, 
as Metschnikoff and others have shown. 
If we accept the theory that the discharge of a colored fluid is a 
method of defense, the question arises, How is that defense ac- 
complished? Does the fluid darken the water in the immediate vi- 
cinity of the Medusa which possesses this power and in that way 
conceal it from its foes, as in the case of the Cephalopoda, or does 
