INTERPRETATION OF FACTS 161 



blastula. Some animals stop growing at this stage. Others continue 

 growing, which means that this single-layered sphere indents and this 

 indentation extends into the sphere until two layers of cells are formed. 

 This is called the gastrula stage. Animals having two layers stop 

 growth when this stage is reached, while all higher forms produce a 

 third layer of cells between these two. 



Every living thing passes through one or more of these develop- 

 mental processes. It was this fact which led so many of the early biol- 

 ogists to suppose that each developmental stage meant that each one 

 of the higher forms of animals must have sprung from those which 

 stopped in the one and two-layer stage just beneath the higher form. 

 What it does mean, however, is that all living forms pass through a 

 similar state of growth.* 



Very early in this development of an egg, after it begins to grow 

 (fertilization apparently furnishes this growth impulse), certain cells 

 divide much more rapidly than do others. The rapid-growing cells con- 

 sequently, soon surround the less-rapidly growing ones, thus forming a 

 sort of protecting case or capsule for them. Now, some of the very first 

 cells that are thus protected and grow into the very innermost portions 

 of the growing embryo, are the egg-cells and the sperm-mother cells. 

 This occurs long before one can even distinguish what kind of an animal 

 .the embryo is to become. 



It was Professor August Weismann of the University of Freiburg 1 

 in Baden, who in 1892 gave the world his book, "The Germ-plasm, a 

 Theory of Heredity," which has made us interpret the various facts so 

 far mentioned in a different way from what had been done before. Up 

 to that time men said that the reason a boy so closely resembled his 

 father was because he was "a chip from the old block," Professor Weis- 

 mann has shown us that this is incorrect, and that both father and son 

 are pieces from the same block. That is, the sex-cells in both mother 

 and father being a part of the earliest differentiation in the growing 

 embryo as already shown, are really placed in position in the child be- 

 fore he is born, so that a parent simply considered as a parent has abso- 

 lutely nothing whatever to do with the matter, such parent's body acting 

 only as a case or capsule which carries the germ-cell to the next genera- 

 tion. 



This is made clearer when it is remembered that every egg in every 

 female is already present at the time of such individual's birth. All that 

 happens during her life is a ripening-, or maturing, of such egg, and fer- 

 tilization by the male sperm. The sperm-mother-cells that are to divide 

 and form sperm, are already present in the male child when he is born r 

 though they begin to divide only after puberty. 



*It does not follow that because a man builds a school, a barn, and a church, that the church 

 must therefore have first been a school and a barn, even though such builder used exactly the 

 same tools and similar material in the building of each structure ; in fact, it would not follow, 

 even though he build the foundation and the first story of each structure exactly alike in each case. 



