388 GENERAL BIOLOGY ' 



Then compare together representatives of groups 5 to 9 

 as to i) diversity of form and habit; 2) resting position in 

 the water. Compare together dragonfly nymphs representing 

 groups 8 (Libellula) and 9 (Gomphus) i) as to form of body, 

 2) form of front of head, and 3) shape and position of feet. 



The record of this stud 7 may consist of brief comparative 

 statements of the things personally observed. State briefly 

 the characters of each type that mark its fitness for the 

 ecological situation to which it belongs. 



Sttidy 4g. A field study of the pond animals in their native 



haunts. 



A pond should be selected that has more or less shore 

 vegetation, and banks dry enough to admit of approach 

 with hand nets. A small pond if permanent is as good as a 

 large one, and if no pond be available, a bay off a lake or 

 river will offer practically the same forms. 



Apparatus needed: Individual dip nets, beakers and 

 vials. A plankton towing net, a sieve net and a few pails or 



bowls for com- 

 mon use will 

 also be advan- 

 tageous. 



Let the collect- 

 ing and study 

 be individual. 



Collect air 

 breathers at the 

 surface with a 

 dip net ; such as 

 are foraging or 

 hiding down be- 

 low may be ob- 

 tained later. 



Fig. 226. Shells of fresh ■water snails, a, Planorbis; 

 b^ Ancylus; c, Limnea; d, Physa. (From Morse's 

 First Book of Zoology, a pioneer American book of 

 nature-study). 



