THE GERM-PLASM THEORY 369 



lias been made in more recent times by Wiesner, De Vries, and I 

 myself. In the meantime we can say nothing more definite aljout 

 the composition of these bearers of life, or ' Ijioi^hors/ as I call them, 

 than that albumen-molecules, water, salts, and some other substances 

 play the chief part in their composition. This has been found out by/ 

 analysis of dead protoplasm ; but in what form these substances are 

 contained in the biophors, and how they aftect each other in order to 

 produce the phenomena of life by going through a ceaseless cycle of 

 disruptions and reconstructions, is still entirely hidden from us. 



We have, however, nothing to do with that here ; we content 



^urselves with recognizing in the biophors the characteristics of life, 



Ind picturing to ourselves that all living substance, . cell-substance, 



md nuclear substance, muscle-, nerve-, and gland-substance, in all 



^ their diverse forms, consist of biophors, though, of course, of the most 



varied composition. There must be innumerable kinds of biophors in 



all the diverse parts of the millions of forms of life which now live 



upon the earth ; but all must be constructed on a certain fundamental 



plan, which conditions their marvellous capacity for life ; all possess 



the fundamental characters of life — dissimilation, assimilation, growth, 



and multiplication by division. We must also ascribe to them in 



some degree the power of movement and sensibility. 



As to their size, we can only say that they are far below the 

 limits of visibility, and that even the minutest granules which we 

 can barely perceive by means of our most powerful microscopes 

 cannot be small individual biophors, but nmst be aggregates of these. 

 On the other hand, the biophors must be larger than any chemical 

 molecule, because they themselves consist of a group of molecules, 

 among which are some of complex composition, and therefore of 

 relatively considerable size. 



It may now be asked whether the determinants, whose existence 

 we have alreadj^ inferred, are not identical with these ' biophors ' or 

 smallest living particles ; but that is not the - case, at least not 

 generally. We c alled determinants those parts of thegerm-sjabstance 

 which determiiie~a ' hereditary character ' of the body; that is, whose 

 presence in the germ determines that a particular part of the body, 

 whether it consists of a group of cells, a single cell, or a part of a cell, 

 shall develop in a specific manner, and whose variations cause the 

 variations of these particular parts alone. 



Again, it may be asked how large and how numerous such 

 ' hereditary parts ' may be, whether they correspond to every distinct 

 part of a cell, or to every cell of the body, or only to the larger cell 

 groups. Obviously the areas which are individually determined from 



