COLLECTING ANIMALCULES. 



destroy all youi' Infusoria. It is also advisable to keep in the vessel 

 a small (^antity of the aquatic vegetation, from among Avhich, you 

 have obtained your specimens. Be careful not to have much, and 

 keep it in a healthy condition. Mr. Vai'ley recommends keeping a 

 small flat water snail in the water, wliich, he states, feeds upon 

 confervae and keeps the water sweet. 



It is usual to give a list of places where Infusoria may be found, 

 but, as some kind or other may be met with in nearly every locality, 

 it is almost useless to insert one, while those ponds possessing certain 

 species, in a few years change, and are no longer to be found in the 

 same places. To Olustrate this, I may mention that some years ago, 

 when preparing for my Natural History of Animalcules, I found the 

 most prolific locality' around London, was Hampstead ; and, accord- 

 ingly, in the summer of 1833, I took a cottage there, to be near the 

 ponds. In some I found beautiful species of the Eiiglena and allied 

 genera, in great abundance, for some years they gradually decreased, 

 and last summer the same ponds I found destitute of that genus. 



The beautiful organisms known under the name of Desmidiece, 

 which form one of the sections of the family Bacillaria, and repre- 

 sented, magnified, in Plates II and XIII, are rarely collected in 

 streams, being unattached. In clear shallow j)ools, on moors and in 

 boggy places, they are generally abundant in summer. They are 

 rarely found in shady woods or deep ditches. To search for them in 

 turbid waters is useless. M. de Brebisson states that, in the calca- 

 reous districts around him (Falaise, l^ormandy) in which the Xavi- 

 culacea abound, Besmidiece are rare. In the water the filamentous 

 species resemble the Zygnema, but their green colour is paler and 

 more opaque. When they occui- ia large numbers, they may be 

 taken up ia the hollow of the hand ; but, when diffused, Mr. Ealfs 

 takes a piece of linen about the size of a pocket handkerchief, 

 lays it on the ground in the form of a bag, and then, by the 

 aid of a tin box, scoops up the water and strains it through 

 the bag. The larger species of Euastrum, Micrasterias, Closterium, 

 &c., are generally at the bottom of the pool, either spread 

 out as a thin gelatinous stratum, or collected into finger-Hke 

 tufts. If the finger be gently passed between them, they wiU rise 

 to the smi'ace in Uttlc masses, and, with care, can be remo-ved and 



