

THE FOUR INSEPARABLE FACTORS OF EVOLUTION. 281 



New hereditary characters appear in the body. 



New hereditary characters reside in the germ. 



The palaeontologist is only observing appearances. From the laws governing 

 these appearances he must deduce what is going on in the germ. It is necegBary 

 for him, therefore, to secure a broad biological foundation for his observation and 

 reasoning and to see how far the phenomena which he observes, or thinks he 

 observes, square with the phenomena observed by special students of ontogeny, 

 selection, and heredity. The body may be distinguished as the soma and the 

 germ as the blastos. To designate new characters which apparently make their 

 first appearance in the soma we may use Weismann's term somatogeni< ; t 

 designate those which so far as we can perceive make their first appearance from 

 the germ we similarly use Weismann's term blastogenic. 



This distinction corresponds with the two great and more or less contempo- 

 raneous movements in living things. 



The first movement (ontogeny), which has been known and observed from 

 very ancient times, is that of the developing organism, its growing and func- 

 tioning body or soma; this movement is called ontogenesis, or individual genesis. 

 These are the visible expressions of the forces, potentialities, predispositions and 

 reactions to environment derived from the germ, or heredity-substance. 



The second movement (heredity), which has been realized as entirely 

 distinct only in modern times, is in the forces, potentialities, and predisposition! 

 of the germ, or blastos. 



Thus the two kinds of movement and genesis of single characters in all living 

 things may be clearly distinguished as 



Blastogenesis, -genie, 



Somatogenesis, -genie. 



The soma (ontogeny) is relatively visible and measurable. It enjoys contact 

 and combat with all the forces of nature, consequently some new characters may 

 arise in the soma. It is also the carrier or vehicle of the blastos, it is the environ- 

 ment of the blastos, or intermediary between the outer environment and the 

 blastos. The forces of the blastos are invisible; in the mammals they are re- 

 motely buried and removed from environment; the blastos (heredity) carries 

 along all characters from generation to generation; it modifies characters; it 

 loses characters; it gains characters. Whereas certain new characters which 

 arise in the soma are merely transient and may not appear in the blastos, we have 

 reason to believe that all new characters which arise in the blastos appear in the 

 soma. Quite marvelous and inconceivable to us is the manner in which the 

 infinitesimally minute blastos can carry the infinitely grand and diverse char- 

 acters of the soma of such animals, for example, as Balamoptera, Elepfms, Homo. 



Still more marvelous and inconceivable is the evolution of the blastos, its 

 incessant change, its gain and loss of characters, always and continuously in the 

 main current of adaptation, or of fitting the soma to its activities and its environ- 



