NUDIBRANCHIATA OF THE L.M.B.C. DISTRICT. 135 
reticulum of mucus with mud and entangled foreign bodies 
in which they remain hidden. In the natural state the 
mucus seems chiefly on the foot and especially at its pos- 
terior end, each individual having a slimy string attached 
to the end of the tail by which it is anchored. This no 
doubt accounts for the manner in which the animal is 
able to live on exposed rocks in the wash of the tide. We 
have several times watched specimens of Ancula in a few 
inches of water when there was a strong tide running past 
the rocks and waves dashing on them and noticed that 
they were swayed backwards and forwards in the water 
but were securely anchored by their tails. 
Transverse sections through the body show that at least 
three different sets of glands connected with the integu- 
ment are present. First there are the mucus-secreting 
goblet cells in the ectoderm which are abundant over the 
whole surface (Pl. VII. figs. 5 and 6, g.c.); then there are 
the distinct glands in the foot (Pl. VII. fig. 5, fgl.) which 
are large and extend for a considerable way into the 
mesoderm ; and finally there are special glands which are 
placed chiefly on the side of the body in its posterior part 
(Pl. VII. fig. 6, gl’.), and in large masses occupying the 
apices of the cerata (Pl. VII. fig. 8, gl’). 
The foot glands are multicellular pyriform masses open- 
ing by narrow ducts on the surface of the foot (Pl. VII. 
figs. 5 and 6, f.gl). The cells are distinctly nucleated 
and granular, and stain deeply with picrocarmine. The 
special glands on the sides of the body and tail consist of 
large single cells of spherical or pyriform shape which 
are generally ageregated ito clumps. These cells are 
distinctly nucleated, but the nucleus is sometimes dis- 
placed to one side and, the greater part of the cell is 
occupied by a clear or faintly granular secretion (Pl. VII. 
fig. 6, gl’). Ducts are not so obvious as in the case of the 
