36 GENERAL EVOLUTION. 



come to be exercised unconsciously, or as habits. The form these 

 habits take, will depend on the opportunities and conditions 

 offered, for instance, in the matter of food, by the surrounding 

 order of things. Motive-force is, of course, only another name 

 for effort and use ; the former being a putting forth by means of 

 conducting material or organs, without executive apparatus ; the 

 latter always requiring organs or parts by which to execute. 



If, as previously assumed, effort and use locate growth-force, 

 cellular structure will appear in the directions indicated by the 

 activity of motive-force. It is converted by protoplasm from heat 

 and chemism, or one only of these. That it does not require dif- 

 ferentiated *^ motive-force" as a source, is proved by the growth 

 of plants, which have no motion proper. 



Growth-force, by its ^^ repetitive " action,* creates organs. 

 These at first will be extremely simple, but, as machines, at once 

 increase the power of the animal to produce motive-force by con- 

 version, whether the machine be a digestive apparatus for the ap- 

 propriation of the material, or a mechanical one for the exercise 

 of the force, the former necessarily preceding the latter in time. 



With the increased power of assimilation (digestion) comes a 

 larger amount of material for increased exhibition of growth-force, 

 a part being burned or otherwise converted into the force, and a 

 part remaining as the material from which the cells are construct- 

 ed. In the latter 23art of the growth-period a considerable portion 

 is usually consumed for motive-force. 



In the history of the material environment, various changes of 

 condition succeeded each other. Changes of level took place ; 

 waters were purified by precipitation of chemical compounds ; 

 fresh waters were established ; the atmosphere deprived of various 

 gases ; new mineral, and especially vegetable, products took their 

 appropriate places. All these offer a vast variety of food-supply 

 and opportunity for the pleasurable discharge of motive-force, and, 

 under the laws pointed out, efforts of animals were directed in va- 

 rious lines, as the conditions presented themselves. Thus execu- 

 tive organs were produced of varied character. Some acquired 

 limbs and others wings for transportation from place to place. 

 What a vast addition to their impressions must have been acquired 

 by the first animals which could thus leave the place of their 

 birth ! How many new "contiguities" were established, and how 



* « 



See " Method of Creation," on the Law of Repetition. 



