The Bill of Fare 71 



extend its boundaries, met the attack of invading and com- 

 peting species, and frequently was forced to retire as condi- 

 tions of soil, climate, and water depth changed. Loosestrife 

 could not remain in deeper water where cattails flourished 

 successfully, and when the depths increased still more the 

 cattails had to give way to submerged plants. 



I thought of these larger plants as I watched the shift- 

 ing which took place. The same alterations occurred in the 

 animal life as well but were much more difficult to see. The 

 cattails and the loosestrife were constantly before my eyes 

 and could be watched, but it was not possible to follow the 

 fortunes of the young catfish and determine accurately their 

 fate. Although I passed through the canal two or three times 

 a week, I never saw them again. But I knew that all such 

 creatures were being constantly harassed. On every trip to 

 the area I saw small fish leave the water in a tiny arc as they 

 endeavored to avoid a larger fish when it made a dash at 

 them. The pied-billed grebes dived continually close to the 

 margins where minnows might seek refuge. Some species of 

 ducks took such food if they could capture it. The herons 

 and the bittern were adept at fishing. I wondered what per- 

 centage of the young catfish became a part of the marsh bill 

 of fare, how many succumbed to such factors as pollution and 

 disease, and what percentage grew into mature fish? And I 

 knew that in this community the problems of all living things, 

 large and small, were similar to those of these catfish. Sudden 

 alterations due to floods, low temperatures, or storms might 

 be a serious threat to the whole marsh. Each radical shift 

 caused destruction, sometimes unseen for a time, which could 

 be withstood only because of the extreme fertility of the 

 survivors. Each considerable change would bring about read- 

 justments with perhaps the disappearance of some forms 

 and an invasion by others. But in spite of these variations the 

 integrity of the community would be maintained, and it 



