343 



As will be seen in the tables that follow, there was noticeable a 

 sharp difference between the rates of increase in the species lists in 

 mid-channel and in the open lake from 1920 to 1922. In fact, substan- 

 tially no. favorable change in number seems to have occurred in the two 

 years in the channel, where decrease in kinds of midges was balanced 

 by increase in worms, leeches, and tolerant snails ; and where, in 1922, 

 the number of all species taken decreased instead of increasing as we 

 proceeded down the lake from Chillicothe. In the wide waters, on 

 the other hand, there was an increase in the list of species in the two 

 years from 11+ to 18+ ; and the increase was almost all due to the 

 multiplication in variety of the less tolerant kinds of snails and midges, 

 (see Table below). Further evidence of improvement in the extra- 

 channel zones is seen as we go down stream (see Table on following 

 page) ; as also in the near to more than doubling of the species lists in 

 size, both in the Rome and the Spring Bay cross-section, as we move 

 outward from the channel into the wide waters (Table on p. 344). 



Summary of Bottom Species Lists, Uppee Peoria Lake, Summer 1922 

 1. comparison with 1920. number of kixds takex 



• The -t- after figures In this and other tables indicates a residue of unde- 

 termined material, definite returns on which might add one or more to the num- 

 ber of species given. 



