136 LIVERPOOL BIOLOGICAL SOCIETY. 
foot glands. At the apices of the cerata the glands are 
much more distinctly arranged in ovate or pyriform masses 
(Pl. VII. figs. 7, 8, 9) and-there are usually distinct 
ducts (Pl. VII. fig. 9, gi’). The cells are smaller, are 
invariably filled with a clear secretion, and the nucleus 
is displaced to the side. We find that the cerata are 
occupied by large blood spaces (the ceratal sinuses, 
Pl. VII. figs. 7 and 8, b.s.) exactly like those of the 
cerata of Dendronotus arborescens.* 
Ancula is not protectively coloured; and as it has no 
cnidophorous sacs, its bright white and yellow colouring 
and conspicuous appearance on dark rocks seemed for a 
time inexplicable. From our experiments we have come 
to the conclusion that it is distasteful to fishes (see below, 
p- 155), and possibly it is the secretion of these large 
compound glands at the apices of the cerata which 1s of an 
offensive nature. 
In Polycera quadrilineata (Pl. VII. figs. 3 and 4) the 
cerata terminating the lateral ridges on the body, which 
we regard as representing the cerata of Ancula, contain 
numerous glands. These are simple pyriform sacs filled 
with large polygonal granular cells which stam deep 
crimson with picrocarmine (Pl. VII. fig. 3, gl). These 
glands open between the ectoderm cells by long narrow 
tubular ducts (Pl. VII. fig. 4). 
In Ancula the large glands in the cerata are somewhat 
different from those of Polycera quadrilineata. 'The masses 
are not so regularly placed and shaped, and the cells are 
not so granular, but seem to a large extent filled up with 
a clear secretion, while the nucleus is displaced to one 
side of the cell. And whereas in Polycera the glands ex- 
tend nearly all over both sides of the cerata, there being 
* Compare our last report, Proc. Biol. Soc., L’pool, vol. iii., Pl. xii. fig. 2. 
