116 E. PENARD ON FRESH-WATER RHIZOPODS. 



large quantity of absolute alcohol so as to kill the organisms 

 instantaneously with their pseudopodia extended.* 



The material settles again very quickly, and I get rid of the 

 greater part of the alcohol, which I replace by a small quantity 

 of borax carmine ■ then after a moment I refill the test-tube to 

 the brim with clean water, I allow it to stand, decant and refill 

 again with clean water and repeat in the same way until, after 

 half a dozen decantations, the deposit is found to be in perfectly 

 pure and uncoloured water. 



I then throw away most of the water and transfer the 

 material to a test-tube much smaller and more convenient, 

 requiring a smaller expenditure of alcohol, and oil. I decant 

 several times with absolute alcohol, then finally replace the 

 alcohol with oil of cloves ; and I have then a collection of 

 rhizopods which only requires sorting, either in a watch-glass 

 or on a slip, and enclosing in balsam according to the method 

 already described. 



The organisms may be preserved for weeks and months in the 

 oil of cloves, and during the summer it is possible to form a series 

 of tubes with the different gatherings and reserve them for 

 mounting as microscopic slides in the winter. 



* This method is still rather defective, as most individuals have time 

 to withdraw their pseudopodia into the shell ; but, as a rule, it succeeds 

 with a certain number of them, and sometimes this denotes a character 

 which might be called specific, some species behaving differently from 

 others. Thus Difflugia snalpellum, that pretty species from the bottom of 

 Lake Geneva, is obtained with its pseudopodia extended easily enough, 

 while others (notably all species with filiform pseudopodia which probably 

 break off) show them very rarely. It is a curious thing that, in these 

 gatherings treated in bulk, Infusoria (those creatures alwa} 7 s so difficult to 

 prepare) are often met with and in a fairly good condition. It was thus 

 that I happened to find specimens of Lio7iotus which lent themselves 

 perfectly to preservation in balsam and showed their long necks well thrown 

 out, which an authority tells me he has never been able to obtain in a good 

 state in spite of the most refined reagents. 



Journ. Quekett Microscopical Club, Ser. 2, Vol. A'., No. 61, November 1907. 



