THE STAGE SETTING 



Eighty per cent of all the eggs were laid in steep elay, and <)S per 

 cent in sloping soil. Thus ho concludes that the egg-laying hahits 

 of these beetles determine tiieir habi- 

 tat, for if they could not get the kind 

 of soil and the slope needed, they 

 would not breed. In this case the 

 fluctuation and distribution of a spe- 

 cies would be dependent upon a single 

 factor. This may be true in the dis- 

 tribution of a great many plants and 

 animals. 



Basic Environments 



There are three states of matter, 

 gas, liquid, and solid. These are evi- 

 dent in the land, the water, and the 

 air in which living things are found. 

 Life is only found in conditions where 

 it is at least partially fitted or adapted 

 to live. These conditions, called factors of the en\iroinnent. are air 

 or its contained gases; water or moisture; temperature; light; 

 chemical constituents in soil, water, or foods; gravity; the presence 

 of a substratum on which the organism rests, such as soil, moving 

 objects in the water, or the sea bottom ; molar agencies, such as 

 wind, water currents, or any moving force in the environment ; and 

 finally, biotic factors which come through the interaction of other 

 organisms in the same environment. 



A birch forest is composed of 

 typical me.sophyte.s. 



Water as a Factor 



Water is absolutely essential to life, from 40 to 95 per cent of all 

 living things being formed of this substance. It is generally true that 

 no growth or life process of either plants or animals can take place 

 without water. An example of this relationship of moisture to life is 

 shown in the story of the British Mu.seum snail related by Mr. Baird.' 



" On the 25th of March 1846 two specimens of Helix desertorum, colloc-ted 

 by Charles Lamb, Esq., in Egypt some time previously, were fixed ui>on 

 tablets and placed in the collection among the other ^h)llusca of the .Musmnn. 

 There they remained fast gummed to the tal)let. About the loth of .Marcli 

 1850, having occasion to examine some shells in the same ca.se, Mr. Il'iird 



1 Ann. Mag. Nat. Hisl. (2) vi. (1850). p. 68. 

 H. W. H, — 2 



