ORGANIC CHEMISTRY AND CELL DIVISION 99 



In different types of cells, all of these stages vary a little as to length 

 of time and as to the method in which and by which particular cen- 

 trosomes, skeins (also called spiremes), spindles, and chromosomes, ar- 

 range themselves. It is well to note also that in the higher forms of 

 plants the centrosomes have not been seen, and that there is a difference 

 between plants and animals in the way the cytoplasm divides. In the 

 animal cells, as shown in the drawing, the cell walls indent until the two 

 indented portions meet, and the separation takes place in that way; 

 whereas, in the plant cell this does not indent, but the cell-wall becomes 

 thicker and thicker until a definite cell wall has been grown for the two 

 new cells. 



There are also exceptions as to just when and how the spindle 

 forms. In some species of salamander, the spindle begins outside of the 

 nucleus, and then as the nuclear membrane disappears the fibers pass 

 through the nucleus itself. 



THE REAL MEANING OF MITOSIS 



The real significance of mitosis is found in the fact that the chro- 

 mosomes, a more detailed study of which will be taken up as soon as the 

 protozoa have been studied, split in two lengthwise and that the chro- 

 mosomes are practically the only visible things that pass from a parent 

 cell to become a new individual. Whatever an offspring is to obtain 

 from its parents must therefore be already present in the chromosomes 

 of the various germ cells of the parents, or it cannot be inherited by the 

 offspring. 



A little later it will be explained also how this lengthwise dividing 

 of the chromosome means that each new individual obtains one-half of 

 whatever it is from its mother and one-half from its father, although 

 one's inheritance on the mother's or father's side is usually not evenly 

 distributed as to quantity, and possibly, quality. For example, we may, 

 as far as external appearance go, resemble our fathers, yet have our 

 mother's mental characteristics. One must therefore not confuse the 

 characteristics which can be seen and are very conspicuous, with those 

 which may not be seen, but which may nevertheless be much more im- 

 portant. 



By remembering this statement one may understand the biologist's 

 division of all cells in the body into two great groups. These two 

 groups are known as somatoplasm ( ) and germplasm 



( ), the latter consisting of those particular cells 



which are going to reproduce offspring like the parent, while the somato- 

 plasm consists of all the other cells of the body. It can be imagined 

 from this that it is quite possible for the somatoplasm or outer portion 

 of the body (which is the only portion visible) to cover up many im- 

 portant or, at least, latent and dormant characteristics that an individual 

 may have inherited, but which characteristics may come forth at .any 



