126 SIDNEY F. HARMER. 
of other marine Ectoprocta® in forming a continuous network 
stretching through the cavity of the zoecium. It usually 
forms a thin layer on the inner side of the ectocyst, and 
another thin layer on the outer surface of the alimentary canal 
and tentacle-sheath, the two layers being connected by the 
network which traverses the body-cavity. A special region of 
this network is often distinguishable as a definite tract which 
passes from the apex of the ceecum of the stomach, in company 
with the colourless retractor muscles, to the proximal end of 
the zoecium. In young zoecia the network is much denser, 
aud the young polypide-buds are constantly enveloped by a 
specially dense concentration of the network. The pigment, 
which is readily soluble in fresh water, is contained for the 
most part in numerous minute granules scattered through the 
funicular tissue, and occurs in two principal colours—purple 
and yellowish brown, both of which may occur in the same 
zoceclum. 
A similar pigment occurs in the growing-points (which are 
very densely pigmented), in the tentacles, round the apertures,! 
and in the ovicells (the young ones being, like the growing- 
points, densely pigmented). It is probable that the pigment 
in all these cases is contained in the funicular tissue, although 
some of it may possibly be in the ectoderm. 
The meshes of the funicular tissue contain numerous trans- 
parent cells, which are colourless or faintly yellow. These 
cells consist of an aggregation of vacuoles filled with a trans- 
parent fluid, and they are often produced into long, fine pro- 
cesses (fig. 192), by meaus of which they are suspended in the 
funicular network. They play an important part in the 
absorption of indigo-carmine, and although not exactly similar 
to ordinary white blood-corpuscles, they will be alluded to in 
the remainder of this paper as the leucocytes. 
These so-called leucocytes have been well figured by 
1 §. delle Chiaje (‘ Mem. sulla Storia e Notomia degli Animali senza Ver- 
tebre del Regno di Napoli,’ vol. iv, Napoli, 1829, p. 147): ‘* Osculis margine 
subfusco cinctis.” 
> Representing these cells after exposure to the action of indigo-carmine. 
