DIURNAL PERIODICITY OF PILOSPHORESCENCE. 25 
Nos. 1, 2 and 3 observed at 6-35 p.m. .... Spontaneous sparking 
(Almost dark outside). in all three, No. 3 
most brilliant. Dish 
lit up in each case 
on stirring. 
Nos. 1 2 and 3 observed at 6-50 p.m. ... All spontaneously phos- 
(Quite dark outside). phorescing most 
brilliantly. 
Also at 1 p.m. to-day, a further supply of Polysiphonia nigrescens 
was collected from the old mooring rope, and examined in the dark room. 
It showed no phosphorescence during the day. On placing in distilled 
water it gives a feeble sparkling, but incomparably less brilliant than on 
similar treatment at night. After dark, from 6-30 p.m. onwards, the 
same sample sparkles when stirred, and a piece put in distilled water lights 
up brillantly all over for from three to five minutes; then the light dies 
away, and cannot further be evoked in that piece by any of the procedures 
mentioned. 
All six of the tow-nettings of yesterday and to-day examined again at 
1-15 p.m.; all spontaneously phosphorescing, and showing up brilliantly 
on stirring. Same result when again examined at 8-40 p.m. 
Friday, September 25th.—Arrived at Biological Station at 4-50 a.m; 
there is just a trace of dawn in the dull, grey sky. Organisms examined 
at once in the dark room, where they have all still been kept over-night; 
all six dishes are flashing spontaneously. 
On standing quietly by and watching the phosphorescence, the minute 
organisms are not moving about rapidly in most cases, and one can observe 
that each active organism is emitting a series of flashes at about the rate 
of one per minute, and between the flashes there is a dimmer light showing 
which regularly becomes increased by a flash. The effect on the eye is 
very similar to that of a revolving light seen at sea at some distance off. 
There is an almost constant dim light lit up by repeated and fairly regular 
flashes. 
Many of the more active organisms are so still that one is able to 
