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THE AMEBIC AN NATURALIST [Vol. XLVI 



saying that BaCl 2 + H 2 S0 4 = BaS0 4 + 2HC1. No one 

 should object to saying that DR + RR = 1DR + 1RR. 

 We push things into the germ cells as we place the 

 dollars in the magician's hat. Hocuspocus! They dis- 

 appear! Presto! Out they come again! If we have 

 marked our money we may find that that which appears 

 from the magician's false-bottomed hat is not the same 

 as that which we put in. But it looks the same and is 

 good coin of the realm. We have a good right there- 

 fore to poke our characters into the germ cell and to pull 

 them out again if by so doing we can develop— not a 

 true conception of the mechanism of heredity — but a 

 scheme that aids in describing an inheritance. We may 

 do this even as we may use algebraical and chemical no- 

 tations, if we remember that x 2 + y 2 does not give us a 

 circle, that a chemical equation does not represent a true 

 reaction or prove the atomic theory, that we have not 

 pulled something new and astonishing out of the germ 

 cell, that a unit factor represents an idea and not a real- 

 ity, though it must have a broad basis of reality if it is 

 to describe a series of genetic facts. 



The facts of heredity that one describes in the higher 

 organisms are the actual somatic characters, variable 

 things indeed, but still things concrete. Their potential- 

 ities are transmitted to a new generation by the germ 

 cells. We know nothing of this germ cell beyond a few 

 superficial facts, but since a short description of the 

 breeding facts demands a unit of description, the term 

 unit factor has been coined. As I hope to show, a factor, 2 

 not being a biological reality but a descriptive term, 

 must be fixed and unchangeable. If it were otherwise 

 it would present no points of advantage in describing 

 varying characters. The only obvious reason for poking 

 it into the germ cell is to distinguish thus the actual 

 parent (the cell) from the putative parent (the carrier). 



■ I hope this statement is not confusing. The term factor represents in a 

 way a biological reality of whose nature we are ignorant just as a structural 

 molecular formula represents fundamentally a reality, yet both as they are 

 used mathematically are concepts. 



