128 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
10 per cent, solution of potassium chromate in 20 mm. thickness absorbs 
the blue, leaving A. 540 to A 505. 
Bright blue filter. — Doppelgriin, SF 0 • 02 grm. dissolved in 100 com. of 
water and in 20 mm. thickness, leaves a narrow red band, a broad green 
band with blue ; and 15 grm. of cupric sulphate dissolved in 100 c.cm. 
of water in 20 mm. thickness, absorbs the red and green, leaving A 526 
to A 458. 
Dark blue filter. — 0*005 grm. of crystal violet 5BO dissolved in 
100 ccm. of water in 20 mm. thickness, and the sulphate of copper solution 
as used above, also in 20 mm. thickness, allow A 478 to A 410 to pass. 
B. Technique.* 
(1) Collecting- Objects, including- Culture Processes. 
Plankton Gathering.! — Mr. G. Murray recommends, for use with 
deep-sea plankton, a cylindrical silk bag, about 1 J ft. long and 3 or 4 in. 
wide. This was tied to the nozzle of the hose, there being a lateral 
overflow vent near the top of the bag. On pumping through this with 
the donkey engine from an intake pipe 8 ft. below the surface, good 
results were obtained. This contrivance enables the operator to work 
while steaming, and is often convenient when the weather is too rough 
for tow-netting. The fixative and preservative employed was a 0 * 5 per 
cent, solution of chromic acid ; good results were also obtained with 
Fleming’s solution, and with platinic chloride of various strengths. 
Culture of Diatoms.! — Dr. H. van Heurck publishes a resume of 
M. Miquel’s admirable methods for the artificial cultivation of diatoms. 
The cultures are divided into ordinary and pure, and subdivided into 
cultures of fresh-water and salt-water diatoms. 
(1) Ordinary cultures of fresh-water diatoms are grown in a 
fluid containing salts and organic substances. The saline nutriment 
is prepared in two solutions : — A. Sulphate of magnesium 10 grm., 
chloride of calcium 10 grm., sulphate of sodium 5 grm., nitrate of 
ammonium 1 grm., nitrate of potassium 2 grm., nitrate of sodium 
2 grm., bromide of potassium 0*2 grm., iodine 0*1 grm., water 100 grm. 
B. Phosphate of sodium 4 grm., chloride of calcium sic. 4 grm., hydro- 
chloric acid 2 c.cm., perchloride of iron liquid at 45° 2 grm., water 
80 grm. These solutions are mixed when required for use, in the pro- 
portion ’of 40 drops of A and 20 drops of B to 1 litre of tap- water, 
and then are added 5 cgrm. of wheat straw and a similar quantity of 
earth moss, previously washed in boiling water. Small cultures may be 
made in wide-necked flasks plugged with cotton-wool ; large cultures in 
crystallisers, or in the square jars formerly used as electric accumulators. 
It is useful to sterilise the fluids in a water-bath for a quarter of an hour 
at 70°. The medium is inoculated with living frustules. The cultures 
should be kept from the sun and exposed to a northern light at 10°— 30° C. 
The growth of green algee may be diminished by reducing the light. 
* This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 
(4) Staining and Injecting; (5) Mounting, including slides, preservative fluids, &c. ; 
(6) Miscellaneous. f Journ. of Bot., xxxv. (1897) pp. 387-8. 
+ Zeitschr. f. angevv. Mikr., iii. (1897) pp. 193-8, 225-36. 
