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 w^ere 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 (PI. VII. fig. b,f.gl.) 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, gV). 



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 aggregated into 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, gV). Ducts are not so obvious as in the case of the 



