Tue Microscope. 281 
and intermixed with Diatomaceous valves, often of extreme 
beauty and rarity, in the deposits (or so called “ earths”) of 
Barbados, the Bermudas and the Nicobar Islands, while an 
entirely new and magnificent deposit was discovered by the late 
Captain Perry, of Liverpool, at Jeremie, Haiti, which contains 
not only a large number of novel species of Polycystina, but 
many entirely new varieties of Diatoms. 
The Polycystinous “earth” should be broken into small 
pieces, about the size of a nut, and boiled for half-an-hour to an 
hour, in a strong solution of common “ washing soda; the 
disintegrated portions being poured off into a large vessel 
containing clean water, from time to time, and the boiling in 
soda repeated, as also the pouring off, until the whole mass is 
perfectly broken up. When the disintegrated matter in the 
large vessel shall have thoroughly settled down it should be 
subjected to several washings, in order to remove the soda, the 
material being allowed to settle thoroughly after each washing. 
It should then be removed to a beaker or wide mouthed bottle 
which should be filled up with water, and after being thoroughly 
stirred or shaken up, the material should be allowed to settle 
for thirty seconds only, and the supernatant fluid and its floating 
particles poured off into a large vessel; this process should be 
repeated three or four times, and will give the heaviest density 
of sand and Polycystina. Repeat this process with the matter 
in the large vessel, allowing it to settle for two-and-a-half to 
three minutes, and the density containing the small Polycystina 
will be obtained. Subject the remaining matter to like treat- 
ment, allowing it to settle in six inches of water for 20 minutes, 
and the density consisting of the debris of Polycystina and of 
Diatoms will result. Now boil each separate sediment in nitric 
acid for fifteen to twenty minutes, remove all trace of acid by 
repeated washings, and finally boil each density in a weak 
solution of bi-carbonate of soda in a test tube of large capacity 
for an hour; this will remove all flocculent matter, and, after 
repeated washings, perfectly clean Polycystina will be obtained. 
The heaviest density consisting of sand and the largest Polycys- 
tina should be placed in a test-tube with about three inches of 
water and subjected to rotatory motion, this will cause the 
Polycystinous shells to rise above, and to free themselves from 
