1914] 
Jackson: Land Viohtebuates of Ridgeway Bog 
repe 7 is, (hmltheria procumhens, Mitchella repens, Betula papip'ifera, 
P()p7ilus cp'andidentata, and Popidus tremidoides. Cornus eatia- 
densis, Acer sacchanmi, and Corylus rostrata are frequent, especially 
near the foot of the hill. The animals of this association are 
even more diagnostic than the plants; eight species are found herein 
that were not observed elsewhere, namely, Buteo platypterus, 
Empidonax minimus, Corvus hrachyrliynchos, Spizella passerina, 
Vireosylva olivacea, Seiunis aur oca pill us, Hylocichki fuscescens, 
and Mephitis ni. fninnesotae ; other species which occur regularly 
are Storeria occipitoniaculata, Cyanocitta cristata, Penthestes atrica- 
pillus, Sciurus h. niinnesota, Peroniyscus ni. gracilis and Lepus a. 
phaeonotus. 
IV. ECOLOGICAL SUCCESSION 
The transformation of a lake into a bog and the general iirin- 
ciple of its accompanying plant succession is a process somewhat 
familiar to most students of ecology and is one which has received 
consideration at the hands of various writers; likewise the ecologi- 
cal succession of animals has been investigated (Adams and 
others, 1909) though to a less extent than that of plants. Not- 
withstanding these excellent contributions, liarely a lieginning 
has been made in the study; detailed field analyses of several 
bogs in each of several widely separated regions, accompanied by 
experimental studies, are necessary before definite conclusions 
can be drawn concerning the causes and processes of ecological 
succession. We have seen in the preceding paragraphs that the 
biota of the Ridgeway Bog area, exclusive of the hillside area, 
may be classified into six ecological associations. These asso- 
ciations are not static; there is a continuous, though slow, invasion 
of each association upon its inner neighbor. That we may more 
clearly understand the physiographic and ecological history of 
this area it may be well to picture it as it probably existed in 
early postglacial times and to trace the various probable stages 
in its transformation from a lake into a bog. 
If one could have examined the shores of the original lake which 
covered the area occupied hy Ridgeway Bog shortly after tlie 
recession of the ice sheet he would jirobably have found it instable 
and subject to weathering, and supporting a little vegetation 
