On the Salivary and Mouth Glands of the Nudibranchiata. 143 
In Sjpurilla the secretory cells resemble those of Doto rather than 
those of Facelina. Fig. II. shows such a cell with the nucleus at one end 
and the streamlets of secretory fluid running to the neck. The cells of 
Galma resemble those of Facelina. In the last-named animal we see three 
phases of secretion represented in Figs. III. and IV. Fig. IV. represents 
the cells in active function ; cells 1 and 2 of Fig. III. shows the phase 
immediately prior to activity, and cell 3 of the same Fig. is probably the 
phase after a prolonged period of activity ; there are two such cells, the 
nuclei of which are labelled 3 ; the nuclei are of irregular shape and 
indefinite outline and resemble the nucleus of the Spurilla cell (Fig. II.), but 
the two cannot represent equivalent phases since Fig. IV. represents the 
actively secreting cells of Facelina, and Fig. II. shows that also the Spurilla 
cell is in full activity. 
. The secretory cells of the mouth glands are thus of at least three types 
one, nucleus large and clearly defined, no nucleolus, perinuclear and peri- 
pheral fibrillae of secretory fluid ; two, nucleus large but rich in chromatin 
and irregularly defined, secretory fluid as streamlets between nucleus and 
neck of cell (e.g., Spurilla) ; three, nucleus comparatively small, poor in 
chromatin ; large nucleolus ; secretion in form of globules scattered in 
form of large sphere around the nucleus and discharged through a 
minute neck. 
If the secretory cells of the mouth glands show a diversity of structure, 
the tubes or reservoirs into which they discharge show an even greater 
diversity. I have already mentioned that the mouth glands are usually 
present as right and left halves opening into a common median duct run- 
ning ventrally to the pharynx and opening into the mouth. The first 
point to be noticed is that the several Eolidids possess tubular mouth 
glands, whereas Dotofragilis has an acinose gland. The second point is that 
the tubes, or at least the common median ducts, are muscular, whereas in 
Doto there are no muscle fibres either in the walls of the separate alveoli 
nor in those of the median duct. The third point of difference is that in 
Doto the mouth gland is only represented by a left bunch of alveoli or 
reservoirs, the right having no chance of any great development since the 
available space on the right side is taken up by the genital organs. 
Besides the bunch of alveoli of the left side there is a glandular tube which 
opens into the median duct at the posterior end of the latter ; it runs 
forwards with the median duct, lying on the dorsal surface of the latter 
and ending blindly just posterior to the opening of the median duct into 
the mouth. This outgrowth is composed of cells which are all glandular 
and has thus a structure not at all comparable to that of the mouth 
gland as exemplified by the left lobe, but it may nevertheless be the 
mouth gland of the right side which has not been developed owing to 
want of space. 
