A Three-fold Development. 14-5 



phyll, therefore protoplasm with the addition of chloro- 

 phyll is the necessary basis of all life. 



All forms of life begin with the single cell, and may 

 come to maturity as a single cell or as an aggregate of 

 many cells. The lowest organism, having but a single 

 cell, performs all the functions belonging to life. It 

 feels, moves, feeds and reproduces its kind. In the many 

 celled organism these functions are performed by separ- 

 ate cells, independent of each other, yet bound together, 

 and all working in harmony with each other. This sep- 

 aration of function is what causes difference in struc- 

 ture, all the various parts of the plant, all the different 

 parts of the animal are aggregates of the wonderfully 

 minute cells, each modified according to the necessities 

 of the different functions performed. The lowest one- 

 celled forms of life reproduce their kind by fission or 

 simple separation of the one mature being into two im- 

 mature beings. All forms of life absorb more nutriment 

 before maturity is reached than is required for the pres- 

 ent support of life, and so they grow. Waste is less than 

 repair, and when the single-celled animal reaches its full 

 size, the excess of nutriment continuing, the cell separ- 

 ates into two immature beings. 



All forms of life above these lowest ones, either 

 plant or animal, have speciallized cells for reproductive 

 purposes. There must be an impregnation of the female 

 germ by the nucleus of the male sperm cell. This pro- 

 cess of impregnation is accomplished in a great variety of 

 ways, but difference in detail does not change the gen- 

 eral statement. There must be a coming together of the 

 two elements, male and female, in order that species may 

 continue to exist. The low algae, the great elm, the 

 sponge and man are all developed from some sort of a 

 germ, which may be called spore, sac, seed or egg. Each 

 of these myriad species of life, in its development from 

 the single egg cell, passes through and shows the ances- 

 tral history of its long descent. The study of embryology 

 makes necessary a theory of evolution of one form or 

 species from another by constant modification. At certain 

 stages of the gTOwth of the embryo of fish, dog or man 

 they are so nearly alike that one cannot be distinguished 



10 



