132 SIDNEY F. HARMER. 
in the leucocytes situated in the growing-points or in the 
younger zoccia, and sometimes in older zoccia. 
No part of the alimentary canal takes up any recognisable 
trace of indigo-carmine. 
6. Bugula avicularia. 
The blue colour is taken up by the leucocytes as in the last 
species. These cells may consist of a comparatively small 
number of large vacuoles (figs. 20, 21), or of a much larger 
number of small vacuoles, or both kinds of vacuole may occur 
in the same cell. In any case the pigment is found diffusely 
colouring the vacuoles. 
The alimentary canal, unlike that of B. neritina, takes up 
large quantities of indigo-carmine (fig. 16). The pigment 
observed in the walls of the alimentary tract is probably 
derived from pigment which has been actually swallowed, as 
those polypides which are still so young that they do not com- 
municate with the exterior have no deposition of pigment in 
their gut-walls. 
The absorption of indigo-carmine takes place in the walls of 
the stomach, cecum, and rectum (fig. 16). No pigment 
appears in the clear area on the inner side of the base of the 
cecum, nor in the wall of the pharynx or of the intestine. 
The indigo-carmine is deposited in granules, which, as may 
easily be seen, are identical with the normal yellowish-brown 
granules; and the admixture of these two pigments naturally 
produces, in most cases, a greenish colour. In young poly- 
pides in which the granules are less strongly pigmented, and 
in the rectum of all the polypides, the bright blue colour of 
the indigo-carmine is not materially altered by the presence of 
any other pigment. 
c. Flustra papyrea. 
Indigo-carmine is taken up by leucocytes which are similar 
to those of Bugula. These cells become intensely blue, the 
pigment being diffused through the cell; darker blue granules, 
associated in some cases with the orange granules already 
