20 ILLINOIS ACADEMY OF SCIENCE 



the same area. Experimental data have also been collected 

 showing the relations of animals to environmental factors, 

 with a view to determining the most effective factors and the 

 best indices of environmental conditions. A long series of ex- 

 periments made by Dr. Shelford and Dr. Allee has shown 

 that fishes are only slightly sensitive to lack of oxygen, but 

 very sensitive to variations in carbon dioxide, the latter being 

 thus the best index to the suitability of water for fishes. As 

 fishes turn back when they encounter unsuitable water, con- 

 ditions which would otherwise be fatal to them are of secon- 

 dary importance. An arrangement of the species studied with 

 reference to their avoidance of water containing five cubic cen- 

 timeters of carbon dioxide per liter — that is, approximately ten 

 parts per million, — corresponds to their arrangement with 

 reference to the distribution of low oxigen and carbon dioxide 

 in their habitats. Similiar results have been obtained with 

 some of the invertebrates. Studies have also been made of the 

 relation of several species of amphibians, insects, and arach- 

 nids to atmospheric conditions. Animals from moist woods 

 hesitate or turn back when they come into air of high evapor- 

 ating power — that is, air which is dry, or hot, or rapidly mov- 

 ing, — while regular residents of open, dry, sandy areas are 

 found to be slightly positive to such air. Animals with sim- 

 ilar integuments die in dry and rapidly moving air in the 

 order of their degree of avoidance of such air. The animals 

 of a habitat agree in respect to the degree of their avoidance 

 of modified air, but not in the time of their survival in such 

 air. 



Dr. Pepoon is busily engaged on a ''Flora of the Chicago 

 Area," to include all plants within a radius of forty miles 

 from the mouth of Chicago River. — that is, from Waukegan 

 to the Indiana line, and westward to the crest of the Val- 

 paraiso morain — approximately to a line connecting Joilet, 

 Aurora, and Elgin. This work will contain maps, photo- 

 graphs of typical ecological regions, discussion of plant as- 

 sociations, and an annoted list. 



Mr. Baker's ecological investigation has taken the form 

 of a paper on the life of post-glacical Lake Chicago, a work 

 which has necessitated a correlation of the life of Chicago 

 with that of all the lake stages from Lake Chicago to the Nipis- 

 sing Great Lakes. The result strengthens a previously pro- 

 posed theory of a post Glenwood low water stage, when the 

 lake was about ten feet above the present datum, and also the 

 presence of an extensive coniferous forest, principally of 

 spruce. Several species, discovered in the Niagara Falls gravel 



