LIFE A DIRECTOR OF FORCE. 



537 



Let the reader examine a living cell in the earliest, or embryonic, 

 stage.* 



The questions which concern us here are — as the chemical sub- 

 stances of the parts of a nucleus have no pov\^er to move or direct them- 

 selves — Whence comes the energy and directivity which compel the 

 granules of protoplasm to form polar star-like bodies? What makes 

 the matter of the chromosomes to form a chain ? Why does the chain 

 break into a constant number of V-shaped parts? Why should they 

 double the number by splitting in halves ? What guides them to travel 

 in opposite directions along the spindle-lines? When they arrive at 

 the poles, what compels them to unite and form the daughter nuclei? 

 Why is all this complicated process necessary in order to make two 

 nuclei out of one? 



Then, lastly, what directs the energy which makes the cellulose 

 build up very differently shaped cells in various places just as they 

 are required ? 



Such are but a few questions which, suggest themselves ; but re- 

 membering that protoplasm and the chromosomes of the nucleus con- 

 sist of the elements 0, 0, H, N, S, and P, and that neither these nor 

 their compounds have any power of self -movement or self -direction, 

 we are driven to the conclusion that life is the director of energy, and 

 acts just as if it were conscious of what it is about, having in view the 

 ultimate forms of cells and the localities where they are to be made. 

 A.S long as any species of plant lives, generation after generation, 

 under the same external conditions of life, the same processes of growth 

 and development and the production of organic substances go on year 

 after year. 



But let us suppose the seeds of a plant find themselves in some 

 locality differently constituted in certain ways — by being much drier 

 or moister, or the temperature on the average higher or lower than 

 that to which the species had been accustomed— what happens? If the 

 change is too great the seedling perishes ; but as a rule plants can 

 stand a considerable amount of differences. That being the case, the 

 seed germinates, and the plantlet begins to " feel " the effects of what 

 Darwin called the * direct action of the changed conditions of life." 

 It responds to them, and, under directivity, it begins to build up new 

 tissues, by making cells to suit the new experiences. 



Thus, if an ordinary terrestrial plant grows up in water, and conse- 

 quently no longer requires the old supportive tissues of the stem, 

 necessary when the plant grew on land in the air, these cease to be 

 formed, as the water now supports it. As the epidermis is no longer 

 required, that, too, fails to appear. We may call such changes 

 " degenerations," but the plant thereby becomes adapted to an aquatic 

 hfe instead of an aerial one. 



Conversely, if a plant has to live, if it can, in a desert, it must store 

 up water against a prolonged dry season and prevent the loss by tran • 



* The whole process of cell- division, or " karyokinesis," is to be found 

 flc.srr:bed in any <;ood text-hook. 



