(139) 
ON THE SALIVARY AND MOUTH GLANDS OF THE 
NUDIBRANCHIATA. 
By T. F. Dreyee, B.A., Ph.D. 
(Read August 21, 1912.) 
The Nudibranchs always have at least one pair of glands in connection 
with the anterior part of the alimentary canal — the salivary glands. They 
may, however, have another pair entering the mouth ; these are of un- 
known function and are sometimes called ptyaline glands. It would be 
preferable, I think, to call them mouth glands until their function is 
known. It has been conjectured that the mouth glands may secrete a 
defensive juice, but as I have never observed a Nudibranch to turn its head 
towards a point of irritation — the papillae are turned in that direction — 
this view cannot well be maintained. A more likely hypothesis is that 
the mouth glands secrete a fluid capable of dissolving the hard parts, 
calcareous or chitinous, of the Hydromedusae on which the " slugs " feed. 
Fig. I. represents the anterior portion of the alimentary canal and the 
attached two pairs of glands as seen in a dissection of Spurilla neapolitana ; 
it is a dorsal view. The mouth gland of the left side E joins with its 
fellow of the opposite side — underneath the mouth — to form a common 
median duct which almost at once enters the mouth cavity A ; the 
salivary gland D runs over the dorsal surface of the crop C, along the 
oesophagus and into the pharynx B ; the ducts of the salivary glands run 
downwards and forwards in the muscles of the pharynx and enter the 
pharyngeal cavity separately, one on each side near the base of the 
tongue. The salivary glands, or their ducts, pass through the nerve 
collar. 
Other animals studied by means of serial sections are : Doto fragilis, 
Faceline Drummondii, Berghia, Calma Cavolinii, Coryphella, Bufibran- 
chialis, C. Uneata, Tritonia pleheia, Marionia, quadrilatera, Favorinm- 
albus, and Bizzolia peregrina. Only Spurilla, Doto, Facelina, Berghia, 
and Calma have mouth glands. 
The salivary glands have the histological structure typical for such 
glands ; they only vary in size and position in the various genera. The 
