2 V.CI' >K I . -Ill I.F<KI>. 



I. IXTRODl ' I K >N. 



In tin- preceding paper we presented rrrt.iin facts concerning 

 ponds, together with a statement of suree^ion in tin- |>ond- ,u 

 the head of Lake Michigan, without entering into its c.uix -. 

 Succession in ponds is due to many causes. It is only under tin- 

 most favorable conditions that we can separate these causes one 

 from another without long and careful investigation. The first 

 attempts of ecologists in this line were considerations of tin- 

 obvious general facts, such as the accumulation of organic detritus 

 and the increased denseness of vegetation. We can give hen .1 

 hint at the more specific changes in the ponds and the relations 

 of these to fish. The subject is one for cooperative, research. 

 At present some of the workers and the necessary funds are not 

 available, and the ponds are being destroyed rapidly. It is 

 therefore improbable that the study can be carried further. Thi- 

 paper deals with the results of a preliminary investigation of the 

 ponds for the purpose of learning something of the causes of 

 distribution and succession of fish and other organisms in ponds. 



II. THK PRESENT CHARACTER AND CONTENT or-~ THE PONDS. 



The ponds with which we are concerned are shown on the maj>, 

 p. 1 31, of the preceding paper of this series. 1 This map i- een- 

 tial to the understanding of the data of the present paper. Tin 

 ponds here considered are an ecological age series, ecological 

 age being determined by a study of amount of sand bottom, 

 humus, etc., as shown in Table I. below. The physiographic 

 history of the region is in full accord with the facts used in decid- 

 ing age though in this case physiographic hi.-iorv is not essen- 

 tial to the decision. The pond designated as I is ecologically 

 youngest, 14 the oldest, and the others intermediate. The 

 measurements, analyses, and quantitative study were carried 

 out on Pond i. ^c (west section), 70, and 146 of the map. Some 

 qualitative records from the other parts of pond 5r, from 5/<, and 

 \4d, are included with those of the ponds in which the oiln-r 

 work has been done. 



See "Ecological Succession," II. BIOL. Hei.i,., Aug., 1911. pp. 1.27-151. 

 Tliese are errors in the pond numbers of this paper which shouM I" corrected. 

 Page 1.52, line 13, for "56" read 58. 

 Pane 133, Table I., last line, last column, for " 15 " read 



