SIR C. ELIOT—REPORT ON THE NUDIBRANCHS. 119 
“(c) Kal el Kebira shoal in Suez bay, among corals. A good-sized specimen 
in which the gills and rhinophores were completely retracted. 
““(d) Reef-edge of Tella Tella Kebira, an island of the Suakim group. 
Gills tripinnate, not retracted. Rhinophores partially retracted. Colour red, 
with mottlings of brown dorsally.” 
All these specimens seem to be Doridopsis rubra. In those dissected the 
cesophagus (as seen dorsally) turns to the right and then forward, describing 
a complete loop and passing under itself. Close to this point are the small 
but distinct salivary glands. After describing the loop the oesophagus 
gradually dilates and runs backwards, tending somewhat to the left until it 
enters the liver. In specimens from other localities which I have examined 
the oesophagus though bent does not form a complete loop. 
The interest of these specimens lies in the fact that they offer a series of 
stages in which a normally cryptobranchiate Dorid becomes almost completely 
phanerobranchiate. There can be no doubt of the reality of the phenomenon, 
for it is vouched for by Mr. Crossland’s notes on the living animals as well as 
by the condition of the preserved specimens. In many species of Doridopsis 
the branchize are habitually everted and not easily retractile into the pocket. 
This seems to be due to the thinness of the integuments. A hard and thick 
gill-pocket forces the visceral mass to find room for it, but when the integu- 
ments which form and surround the pocket are thin membranes, the visceral 
mass tends to expand beneath it and to press its floor upwards. The branchiz 
are thus driven outwards, and doubtless the more they are exposed the hardier, 
thicker, and larger they grow, and therefore it is more and more difficult. to 
find room for them in the delicate pocket which gradually becomes disused 
and atrophied. In one of the present specimens there is no sign of the pocket 
except an inconspicuous circular fold of skin running round the base of the 
stout branchial plumes. The rhinophore pockets, though plain in some 
specimens, seem to have altogether atrophied in others. 
Tt seems natural to suppose that the phanerobranchiate condition is the 
more primitive and that the branchial pocket is a later specialization, 
but these specimens indicate that in some cases at any rate variation may 
take the opposite direction and that cryptobranchiate forms may become 
phanerobranchiate. 
Dorimopsis NIGRA (Stimpson). 
(See Eliot, Proc. Zool. Soc, 1904, vol. ii. p. 275, and authorities there quoted.) 
Several specimens from the mud-flats near Suez, where the animals were 
found under stones and in the cavities of a red sponge which they probably 
eat. They were also found with orange-coloured egg-ribbons which they had 
probably laid. All the specimens appear to belong to the smooth black 
variety, which has no spots but a light border round the mantle and foot. 
