938 
THE VOYAGE OF H.M.S. CHALLENGER. 
distribution. On one occasion in the Western Pacific a dozen of each of these species 
were separated out by means of pipettes and put into separate globes of pure filtered sea 
water. In the evening, when the water was disturbed, about a dozen spots of very 
brilliant phosphorescence were observed in each of the globes ; no difference could be 
observed in the light from the two species. They ceased to give out light when dis- 
turbed three or four times in succession, but after an hour’s rest light was given off as 
brilliantly as at first.” 1 
Coccospheres and Rliabdospheres. — The nature of these organisms is very obscure, 
as from their minute size accurate observations are extremely difficult. They are 
abundant in all surface and subsurface waters 
of tropical and subtropical regions away from 
the influence of coast waters, and are most 
frequently observed entangled in the proto- 
plasmic matter of pelagic Foraminifera and 
Radiolarians, in the stomachs of Salpce, of 
Crustaceans, and other pelagic animals ; they 
can, however, with difficulty be collected 
floating free in the water. They were not 
observed in the Southern Ocean south of the 
latitude of Kerguelen, nor were their broken 
down parts found in the deposits south of 
that latitude. Rliabdospheres are almost ex- 
clusively met with in water above a tempera- 
ture of 65°, while Coccospheres are frequently 
found in water as low as 45° ; indeed the Cocco- 
spheres are larger and more numerous outside of the tropics. . Rhabdospheres are never 
1 Mr. J. T. Cunningham says : — “ The specimens of Pyrocystis noctiluca preserved in glycerin were mostly collapsed, 
the membrane or outer capsule being wrinkled, hut on the addition of water they at once became spherical. Addition 
of iodine dissolved in potassium iodide on a slide produces no effect either on the membrane or cell contents beyond 
tinging them slightly yellow. When a drop of sulphuric acid has been added previously, dilute iodine solution produces 
a very marked effect; a number of the cells become a beautiful deep transparent blue, but some become reddish purple. 
Occasionally one specimen is partly blue and partly purple. When strong sulphuric acid is added to some specimens 
on a slide, they remain unchanged for some time, then gradually the membrane becomes thinner and to a great extent is 
dissolved away. Even after twenty-four hours there was left a residue of the membrane very small in quantity, 
retaining to a slight extent the shape of the membrane, and consisting of very minute granules. After boiling a large 
number of specimens in a watch-glass with nitric acid for some minutes I could find no residue at all of any kind. When 
burned on platinum each specimen leaves a circular stain. 
“ As compared with the capsule of Ceratium, the membrane behaves under the influence of iodine in exactly the 
same way, but it resists to a much greater degree the action of strong sulphuric acid. The capsule of Ceratium in the 
acid breaks up into pieces and disappears in less than a minute. The complete disappearance of the membrane of 
Pyrocystis in boiling nitric acid makes it improbable that there is any silica present ; if there be any it must be in 
very small quantity ; it certainly does not form a continuous skeleton. It is most probable that the membrane is com- 
posed of a peculiarly resistant form of cellulose, closely similar to the modification which forms the capsule in Ceratium, n 
Fig. 339. — A Coceosphere ; 1000 times the 
natural size. 
