SIR C. ELIOT—REPORT ON THE NUDIBRANCHS. 105 
brilliant blue-green flash of light comes from the gills of each specimen. 
The gill is shown up plainly, and shown to be half-contracted. The light 
comes from the finer branches, and the larger ones show dark against the 
light. On flicking the water the light ceases to be shown after the second or 
third time. If now any part of the body is touched a brilliant series of rapid 
flashes lasting up to five seconds appears from the gills, the effect being like 
miniature tropical summer lightning. This also ceases to be shown after the 
third or fourth irritation. The animal may take to swimming, and then 
clouds of luminous mucus fill the water with light. 
“The strong irritation of a fresh specimen results not only in the main 
display from the gills, but also a milder yet brilliant and steady light is 
emitted from the edges of the tail, dorsal crest, and various points and 
processes of the body.” 
GONIODORIS CASTANEA, Alder § Hancock. 
(Alder & Hancock: Monograph. Fam. I. pl. 19, 1846. Bergh: “ Die Gattung Gonio- 
doris,” Malac. Blatter, Neue Folge 2, 1880, p. 126. For the genus see Eliot: 
Journ. of Conch. vol. ii. Oct. 1905, p. 243.) 
Sent to Mr. Crossland by Mr. J. G. Logan of Suez. No notes except the 
label “ Nudibranch among compound ascidians.’”’ Five specimens, of which 
the largest is 10 mm. long, 5 mm. broad, and 4:3 mm. high. The others are 
much smaller. All are yellowish brown with markings of darker brown, and 
in all of them portions of the viscera show conspicuously through the semi- 
transparent skin as of a deep blue-black. The foot is broad, wider than the 
body, and the tail bears a well-developed ridge. At the side of the head 
are large lobes as usual in the genus. The dorsal margin is raised, forming 
a distinct rim all round the back. Down the middle of the back, from the 
rhinophores to the branchie, runs a ridge. In some but not all of the 
specimens there are other inconspicuous projections on the back which may 
be artificial puckers or accessory ridges. The rhinophores are set far 
forward : they are rather large, non-retractile, and bear about twelve 
perfoliations. The branchize also are non-retractile, seven in number, stout 
and tripinnate. In some specimens they are tipped with dark pigment. 
On opening the body the liver is found to be of a deep dark green colour, 
covered in parts but not everywhere with the bright light yellow follicles of 
the hermaphrodite gland, which contrast with it vividly. 
In the central nervous system the cerebral and pleural ganglia are closely 
united, and the pedal separate, so that there seem to be only two pairs of 
ganglia in all above the esophagus. The eyes are large and black, set on 
short stalks. The commissures are short. 
No labial armature in the ordinary sense was found, but on the lips are a 
number of dark ridges and prominences, which perhaps are the structures 
