THE ORIGIN OF LIFE 139 



ponents or organelles, which are seen to be individually self- 

 perpetuating by means of growth and division. The typical cell 

 nucleus, as is well known, is a spherical vesicle containing 

 a semisolid, diphasic network of basichromatin (formerly 

 "chromatin") and oxychromatin (linin) suspended in more 

 fluid medium or ground called nuclear sap. When the cell is 

 about to divide, the basichromatin resolves itself into a defi- 

 nite number of short threads called chromosomes. Now, 

 Boveri found that, in the normal process of cell-division known 

 as mitosis, these nuclear threads or chromosomes are each 

 split lengthwise and divided into two exactly equivalent halves, 

 the resulting halves being distributed in equal number to the 

 two daughter-cells produced by the division of the original 

 cell. Hence, in the year 1903, Boveri added a fourth article 

 to the law of genetic vital continuity, namely: Omne chromo- 

 soma ex chromosomate. 



But the law in question applies to cytoplasmic as well as 

 nuclear components. In physical appearance, the cell-body or 

 cytoplasm resembles an emulsion with a clear semiliquid ex- 

 ternal phase called hyaloplasm and an internal phase consist- 

 ing mainly of large spheres called macrosomes and minute 

 particles called microsomes, all of which, together with 

 numerous other formed bodies, are suspended in the clear 

 hyaloplasm (hyaline ground-substance). Now certain of 

 these cytoplasmic components have long been known to be 

 self-perpeticating by means of growth and division, main- 

 taining their continuity from cell to cell. The plas- 

 tids of plant cells, for example, divide at the time of cell- 

 division, although their distribution to the daughter-cells does 

 not appear to be as definite and regular as that which obtains 

 in the case of the chromosomes. Similarly, the centrioles or 

 division-foci of animal cells are self-propagating by division, 

 but here the distribution to the daughter-cells is exactly equiva- 

 lent and not at random as in the case of plastids. In the 

 light of recent research it looks as though two other types of 

 cytoplasmic organelles must be added to the list of cellular 



