ADJUSTMENT OF ORGANISMS TO ENVIRONMENT 389 



Sweep the open water with the dip net for free swimming 

 forms. (Most of these are obtained more readily with a 

 plankton net.) 



Sweep the submerged vegetation with the dip net for the 

 climbing and clinging forms ; some members of groups 2 and 

 3 will thus at the same time be obtained. 



Scrape the bottom with the dip net for bottom forms; 

 scrape deeper and sift out at the surf ace, to get the bur- 

 rowers; for these a sieve net is more efficient. 



Take up submerged sticks, stones, leaves, etc., from the 

 water and examine them for attached forms (the examina- 

 tion is very satisfactory by submersion in water in a big 

 white bowl; bryozoan colonies (see fig. i88a) will, however, 

 be easily seen without this submersion. 



Study each species as it is obtained ; put a few specimens 

 into a beaker of clean water with a few clean pebbles on the 

 bottom and some stems at one side and watch it. Determine 

 to which of the nine groups it belongs and write its ecological 

 characters in the proper place in a table prepared with the 

 following column headings : 



Name. 



Stage (larva, pupa or adult, etc.) 

 Feeding habits. 

 Takes air how. 

 Swimming apparatus. 

 Clinging or climbing apparatus. 

 Means of locomotion other than swimming. 

 Means of J observation of enemies 



escaping | attack of enemies 





It should be possible to obtain: 



Of group i, water skaters, water spiders, springtails,etc. 

 Of group 2, whirligig beetles. 



