NET DETERIORATION IN LAKE ERIE 



159 



to describe a cotton fiber briefly. Imagine outside pressure applied to 

 a very heavy walled rubber tube which thereby collapses and thus 

 acquires a cross section somewhat dumb-bell-like in form. The wall 



Figure 6.— Cotton fiber in nonsterile tap water. Decomposition has started 



of a cotton fiber varies in thickness and is most often without structure, 

 though pits and pores are sometimes visible. The interior of the fiber 



Figure 7.— Cotton fiber in lake water plus slime from nets. Numerous bacteria are 



present 



is lined with dried protoplasm, which may serve as a food for bacteria 

 penetrating within. 



Figure 8.— Same as Figiue " except in Dubos medium. The bacteria have pene- 

 trated the lumen of the fiber and destruction is practically complete 



The air-filled lumen appears dark in the pictures until enough de- 

 terioration takes place to allow water to enter and fill the gap, where- 



