68 NILS HJ. ODHNER, MOLLUSCA. 
thus, of a more considerable length in the present species than in most of the Aeoli- 
didae, and it is, and more so the stomach, wider than the liver duct (see below). 
The intestine has no internal fold such as is described in the case of Aeolis by 
HEcCHT (1895), but only a number of plications of its walls throughout. 
On the under side of the stomach, in the middle of its length, debouches a 
narrow, very long, liver duct (d.), which leads from the posterior part of the body 
behind the rectum, where it springs from the principal liver trunk. This stretches 
Fig. 22. Nervous system of Madrella ferrugi- 
nosa A. & H. b. buccal ganglia; c. cere- 
bro-pleural ganglia; g. genital nerve; o eyes; 
p. pedal ganglia; st. statocyst; I rhinophor- 
ial nerve with ganglion olfactorium ; 2 nerve 
to the tegument of the head; 3 small nerves 
to the upper part of the oral veil; 4nerves 
to the lateral parts of the oral veil; 35 cir- 
cumbueccal nerve; 6 anterior lateral nerve; 
7 latero-pallial nerve; 8 anterior pedal nerve; 
9 posterior pedal nerve; 10 pallio-dorsal 
nerve. 
Fig. 23. Genital system of Madrella ferru- 
ginosa A. & H. g. hermaphrodite gland; 
gl. mucus gland; o. d. oviduct; p. penis 
sheath ; r.s. receptaculum seminis; v. vagina; 
v.d. vas deferens; v. s. vesicula seminalis; 
3 male, 9 female genital orifice. 
backwards in the median line, with numerous branches, and from its anterior end there 
emerges one lateral trunk on each side, proceding forwards and branching into the 
anterior and lateral portions of the notaeum. This liver system (l.) differs consi- 
derably from that of the whole group of Aeolidioidea (Ert1otT 1910), even from those 
forms belonging to it which have the liver diverticula partly retained in the body, 
partly in the cerata (Janidae). In Madrella ferruginosa the liver is entirely enclosed 
in the body and sends no branches into the cerata.' Further the liver is, as a 
whole, trilobed, and debouches into the stomach by means of a single duct (d.). 
This last-named condition separates Madrella from as well the Aeolidioidea as the 
family Pleurophyllidiidae, where three liver ducts (one median and 2 lateral) debouch 
1 Euror (1902) states that very short diverticula of the liver penetrate into the cerata: in 1903 he finds 
them empty. 
