153 



Aquatic Organisms 



levels of shrubs, and numerous orchids occupy the sur- 

 face of the bog beneath and between the shrubs. 

 Willows and alders fringe all the streams, associated 

 there with a host of representatives of other families 

 crowding down to the waterside. A few of these on 

 account of their usefulness or their beauty, we shall 

 have occasion to consider in a subsequent chapter. 



Such are the dominant aquatic seed plants in the 

 Cayuga Basin; and very similar are they over the 

 greater part of the earth. The semi-aquatic represen- 

 tatives of the larger families are few and differ little 

 from their terrestrial relatives: the truly aquatic 

 families are small and highly diversified. 



ANIMALS 



ANY of the lower groups of 

 animals are wholly aqua- 

 tic, never having de- 

 parted from their ances- 

 tral abode. Other groups 

 are in part adapted to 

 life on land. A few 

 others, after becoming fit 

 for terrestrial life, have 

 been readapted in part to 

 life in the water. Aqua- 

 tic insects and mammals, 

 especially, give evidence 

 of descent from terres- 

 trial ancestors. As with 

 plants, so with animals, it is the lower groups that 

 are predominantly aquatic. The simplest of animals 

 are the protozoans ; so with these we will begin. 



