108 E. PENARD ON THE COLLECTION AND PRESERVATION OF 



the mouth of the test-tube, the water rushes in, carrying with 

 it the surface-mud, which is always the richest in organisms 

 of all kinds. Then I empty the contents of the test-tube into 

 a larger receptacle — a wide-mouth bottle perhaps, or a long tin 

 canister which I carry with me. After this I begin to fish 

 again, plunging my tube sometimes here, sometimes there, 

 especially in those places where the yellow, brown, or greenish 

 felt of the bottom is thickest, each time emptying the contents 

 of the test-tube into the receptacle. 



When the latter is full, I allow the sediment to settle for two 

 or three minutes, and then I decant, pouring off the clear part 

 of the liquid and returning the deposit into the same test-tube 

 which I have just been using. The latter, well corked and 

 wrapped in a piece of damp linen, goes into my pocket, and 

 the gathering is made; it only remains to find another pool 

 and to fill a second test-tube. 



On returning home I empty my test-tube into a jar full of 

 clean water ; but I usually take the precaution of passing the 

 collection through a wire gauze sieve with a ^-nim. mesh. The 

 largest rhizopods easily pass through the mesh,* and the 

 coarse deposit (algae, small molluscs, vegetable threads, etc.), 

 which hinder examination considerably, remain on the sieve. 



When the bottom of the marsh is covered by a close carpet 

 of aquatic mosses, collecting is simpler still. It is quite enough 

 to take a handful of mosses, green and free from mud if possible, 

 and wrap it up in wet linen. It will then only be necessary to 

 shake the mosses in a pot filled with water, and to turn the 

 contents of this pot into a jar previously covered with a wire 

 sieve. 



The aquatic mosses, when they form a thick carpet, are often 

 very rich in organisms of all kinds, and rhizopods show them- 

 selves in quantities. Richer still are the tufts of sphagnum, 

 where these animals are always extraordinarily numerous, 

 represented most often by particular species, mainly of the 

 large family of the Nebelidae. 



If now we suppose that we have to do with a large lake, and 

 we wish to take a gathering at a depth of 10, 20, 40 metres, or 



* With two or three exceptions, more particularly among the species 

 from the great depths of lakes, where, moreover, owing to the fineness of 

 the mud particles, sifting is useless. 



