1901) MICROSCOPICAL JOURNAL. 219 
which: to strain out large pieces of dirt. The material is 
strained into one of the porcelain or other dishes, and 
after an interval of not more than half a minute the dish. 
is inclined to one side, a gentle rocking motion being 
given at the same time. Any desmids will collect in a 
bright green line or patch at the edge of the receding 
water, from which they are picked up by means of the 
pen-filler. By working the water round the edge of the 
dish the desmids may be drawn into green patches in 
almost. any desired part of the vessel, and one lot after 
another picked up until there are none worth troubling 
about, As the desmids are removed they are transferred 
to the pomatum-pot, where a drop of Zenker’s fixative 
suffices to fix them. Zenker’s fixative is made up of 5 
per cent of sublimate and 5 per cent of glacial acetic 
acid dissolved in Muller’s solution, which is itself 
composed of two to two-and-a-half parts of potassium bi- 
chromate, one part of sodium sulphate, and a hundred 
parts of water. A repetition of the rocking process 
enables the desmids to be again collected, taken up with 
the filler, and transferred toa dish of clean water, being 
deposited in a patch near the edge of the dish. This 
latter is again rocked to wash away the fixative, together 
with any foreign matter that has survived the previous 
process. The desmids should be again transferred to 
clean water to ensure the removal of any trace of fixative, 
and if they are to be stained the stain can be washed 
away in the same manner. This method of washing in- 
_ volves less loss of specimens than the ordinary decanta- 
tion method, providing that care be taken to deposit the 
desmids as close together as possible after each trans- 
ference; whilst the process does not take more than from 
half an hour to an hour, so that the fixative has not time 
to injure the color of the specimens. If much foreign 
matter—e, g. peat—is mixed with the original gather- 
ings, the whole may be left in a wide-mouthed bottle in 
