APLYSIID A. 61 
edge numerous glands secreting the purple fluid. Posteriorly the 
mantle spreads backward in a folded tongue or lobe, the excurrent 
siphon; at the base of this opens the anus, either as a pore ora 
short tube. Under the right side of mantle lies the gill, a single 
lunate plume. In pl. 35, fig. 52, the margin of the mantle is shown 
by the dotted line m m. Under its anterior right edge is seen the 
genital orifice, continued in the genital groove, gr.; behind this at 
o is seen the orifice of the opaline gland. 
The Opaline Gland (variously known as the “ grape bunch-shaped 
gland,” “ gland of Bohadsch,” etc.) is a rather large body, sometimes 
consisting of numerous oval unicellular glands each with its inde- 
pendent efferent duct (pl. 33, fig. 25), but usually composed of a 
a grape bunch-like mass of cells communicating with a common 
cavity, opening externally by one orifice (pl. 33, fig. 24). Three 
sorts of cells compose it: odoriferous cells, color-secreting or pur- 
purigene cells, and giant mucus cells; the first two present the 
same histological features, the protoplasm being granulose, the nu- 
clei generally visible ; in the mucus glands the protoplasm is homo- 
genous, nucleus not always visible. The gland secretes three 
liquids: a white and odorous fluid which imparts to Aplysia its dis- 
gusting smell, a violet and a mucous substance. In some species 
the violet secretion is wanting. Morphologically the gland is 
similar to the purple-secreting glands of the mantle. It is ecto- 
dermal in origin, innervated from the pedal ganglion, and its special 
function is apparently the secretion of odorous fluid for defensive 
purposes. It seems to be special to the Ap/ysiide, and probably 
has no homologue in the Cephalaspidea. 
The radula in Aplysiide is broad, somewhat lance-head shaped 
(pl. 33, fig. 23; pl. 9, fig. 18, 14), composed of many rows of nu- 
merous, nearly similar teeth with denticulate cusps, the rachidian 
tooth being wider, with bilobed spreading base. 
In Tethys the teeth have long cusps, closely serrate on both outer 
and inner sides (pl. 9, figs. 11, 12, T. punctata). 
In Dolabella the radula is extremely peculiar, the teeth being all 
unicuspid, very narrow, not serrate. See under sub-family Dola- 
belline. 
In Dolabrifera the denticles on the cusps are few, laterals 
mostly tridenticulate, with no denticles on the inner margins of 
cusps. 
In Petalifera the radula is considerably like that of Dolabrifera 
(pl. 55, fig. 12, P. virescens). 
