THE WATEK-CRESS SOVVliUG. 15 



iire the I'lvsh-wiitrr Uillitlslu's FiiiitliilKs iinhilus. /'. tliiiitliiiii ii---. and /•'. tli.siKir. 

 The first occurs troiii Michigan to Ahabama, Mississippi. mikI Texas, and is 

 rather conuuon in aiiiall lowland ponds. The second is idiiiKl from Maine to 

 North Carolina in river months, in the Great Lalves. and in practically all ot 

 the small lakes in the upper Mississippi Valley. The third occurs in smaller 

 lakes and ponds from northern Ohio to Illinois and south to Mississipi)i. 

 Spe<-imens of each of these species could be obtained at any one of several 

 small lakes in the northern part of Indiana. 



It is probable that some of the oatfishes might also be useful in this connec- 

 tion, and it is suggested that it might be worth while to try one or more of 

 the small species known as '"mad Toms." belonging to the genus SchUbeodcf;. 

 One or more species of this genus can be found in almost any small, sluggish 

 stream in Pennsylvania. Virginia, and West Virginia. 



The writer believes that carp .should prove of value in keeping 

 down this cress sowbug. there being one drawback, however, that the 

 carp must be watched to see that the}' do not develop too rapidly 

 and that thej' do not attack the cress or make the water muddy. Cat- 

 fish have been tried and found wanting in the case of the water-cress 

 leaf-beetle, which will be considered elsewhere (pp. 16-20). 



