Defence among certain Meduse. 345 
bell of genera like Gemmaria and Willia. In Athorybia 
also the rows of so-called nematocysts on the outer walls of 
the covering-scales do not in many cases show the “ fil dun 
nematocyste,”’ and therefore we may well question whether 
they are functionally nematocysts, lacking as they do this 
characteristic internal organization of these organs. Still the 
homology of these structures with nematocysts is an open 
question, and it remains yet to be seen whether they might not 
be regarded as lasso-cells in which certain parts have suffered 
a change in form. 
There seems nothing to prevent our accepting the theory 
that the “corps sphériques” of the above description are 
homologues of nematocysts, and Bedot’s figure, as far as it 
goes, does not disprove that they are these organs even if the 
central ‘“ thread’ is absent. 
Between these spherical bodies, however, and the pigment- 
pouches or glands Bedot thinks it necessary to recognize a 
distinction, and certainly their form is very different and 
justifies his views in this regard. Moreover the pigment- 
glands discharge their contents, whereas the spherical bodies 
do not have this power. Is there, however, anything to show 
that the pigment-glands are not more completely developed 
clusters of the so-called spherical bodies? and may not the 
pigment-gland be formed by an aggregation and maturation 
of the spherical bodies? Such an interpretation was given 
the coloured bodies when I studied them, and there is no new 
evidence to lead me to abandon my former opinion. ‘The 
‘‘ pigment-spots”” were at that time regarded as remotely 
represented in Apolemia “‘ by elevations composed of clusters 
of cells on the surface of the tract.”” My use of the word cell 
with two meanings, one as a lasso-cell and the other asa 
histological cell, has led to a confusion and a just criticism 
by Bedot. I consider the pigment-glands to be formed of an 
aggregation of nucleated cells, and each pigment-spot to be 
comparable to a nematocyst (lasso-cell). 
In some genera irritation of the animal leads to a change 
in colour of the covering-scale, which may be akin to the 
discharge of pigment from these bodies. This phenomenon 
seems also to be connected with pigment-cells in the organs, 
although the character of these structures has not been fully 
described. 
Dr. Carl Chun mentions a change of colour of the covering- 
scales in Ceratocymba spectabiiis from the Canaries. He 
speaks of this phenomenon in the following manner :— 
“Sehr eigenthiimlich verhiéit sich das Deckstiick bei 
stiirkerer Beriihrung, insofern auf einen Reiz hin zuerst in der 
