68 Kansas Academy of Science. 



The preservation of many species through long geological ages must, in many cases, be 

 due to this law ; but the opposite condition of the rapid changing of food, fitful and 

 inconstant conditions, the rapid succession of extremes, will necessarily destroy life, and 

 cause the extinction of a species depending upon it. The mean condition of slow, per- 

 sistent deviation will cause modification and adaptation of structure, and consequent 

 preservation of life. Almost any species can tolerate a very slight alteration of its food 

 with little inconvenience ; and a persistence of the change, inducing a tendency in a 

 certain direction, will inevitably bring its appropriate modification of animal structure, 

 through the simple law of adaptation of form to environments. Food being an import- 

 ant environment of every animal, change in its conditions must enforce change upon 

 the animals depending upon it. Food-selection acting as a persistent, moulding force 

 upon a mutable recipient, the animal organism, the result of its influence in every 

 movement must be alteration of the organism towards the direction of least resistance. 

 This direction of change must be thg one of conformation to the new condition, and 

 adaptation to the new characteristics of the food as presented. 



Every species must be capable of converting all food into nutriment that lies within 

 a certain range and limit, and the widening of this limit is a comparatively easy opera- 

 tion. Its extension in a certain direction and contraction in another will, by a continual 

 succession of such movements, bring a total and complete change of form. Branching, 

 deviation by a few groups of members of a species in different directions, may give rise 

 to different forms, and in time become established as forever separate species. 



The factors that enter the arena as active causes of the phenomena of changes in the 

 all-potent food environment, are numerous and variable. In the vegetable world, upon 

 which all animals depend for their food either directly or indirectly, the causes inducing 

 its variation as a food are legion ; and in the present state of our knowledge very few 

 are even partially understood. There arc forces and inter-force.s, acting variously and 

 erratically, so that in the main we can comprehend but little of their Avorkings. 



Cosmical influences have determined the quantity and quality and the main charac- 

 teristics of the plant world from the beginning, and through it of the animal world. In 

 the earliest history of the earth, when it was just sufficiently cooled from its cosmical 

 fusion to be habitable for the earliest forms, these were such forms and manifestations of 

 life as the conditions induced and permitted. The meager and lowly-organized animal 

 life was moulded to and subsisted upon the vegetable life which was its cotemporary. 

 This plant life existed undoubtedly — indeed, mv^t have existed — in order to make ani- 

 mal life possible, as the latter unquestionably depended from its genesis upon the plant 

 life coexisting, even though they may have been evolved simultaneously from the pri- 

 mary protoplasmic substance which is the mysterious basis and origin of all organic life. 

 Food-selection, at the first, touched the shadowy, unknown beginnings of life; and has, 

 from its very threshold, held all life in its jjowerful embrace, molding it as the sculptor 

 does his clay! 



Whatever the subtle influences may be, so mysterious yet so potent and forceful — be 

 it peculiarities of soil or air, inconstancy of the methods of fertilization, fortune or mis- 

 fortune in the struggle for existence — whatever the quiet, irresistible force may be that 

 induces a change in the quantity or quality of a plant as a food for a species of animal, 

 when the change comes the animal must change with it or perish. Suppose a peculiar 

 quality is developed in a plant in a particular locality, and the animal there making it 

 its habitual food prefers the change and follows it closely. Preference leads to habit, 

 variation is begun, natural selection seizes the new tendency, and by the power of food- 

 selection modifies the animal economy to the new food. The same species in another 

 locality may have its food suffer from some influence so as to cause deterioration and be- 

 come unfit for use, and compel it to adopt a nearly allied plant. This plant having 

 previously been but occasionally used for food, its entire adot)tion would "cause some 



