No. 642] SEROLOGICAL REACTIONS' 



95 



more supplementary or fluctuating components ; chemical 

 groups which represent the more constant features of 

 organization coupled with subsidiary groups of more re- 

 stricted significance. That is, there seem to be series of 

 substances of like chemical constitution common to all 

 the cells of an organism, possibly to even various groups 

 of organisms, and superimposed upon these central or 

 foundational constituents, probably as parts of the same 

 molecules, are secondary systems, or ])()ssihly systems 

 within systems, whicli modify tlic main (Mmfiu-in-ntions in 

 various ways. 



This conception cei'tainly scjuares with the fact that 

 degrees of specificity paralleling the kinships of animals 

 may be shown by immune sera. It harmonizes with what 

 we know of the architecture of the native proteins as well 

 as with our whole scheme of natural biological taxonomy 

 in which we find certain fundamental stable featuries 

 representing a broad series of organisms, and less and 

 less inclusive characteristics which grade down to the 

 minor differences that separate species, varieties and in- 

 dividuals. Nor is it incompatible with what we know of 

 chromosomes and genes. The very fact that heritable 

 grades of a single gene in a given chromosome mav occur 

 {e.o.. in Drosophila) and that one of these variants may 

 m turn be modified gradationallv bv a series of secondary 

 factors located in other chromosomes snii-uests the type 

 of oro-nnization .]ust discussed. 



^\ ith the remarkable and al)iui(l;iiit ex ulciic' ot liaml- 

 and-dove relationships betwoni unit cliaractn > and 

 cln-omoM.mos fliat Ims hoon iiccnmulated m recent years 

 tlirou-li 111.' p;iiMst:ikin-' stiidu's of workers on Droso- 

 pliild nnt to mciilioii dt Imo- corrohnrntive work, it seems 

 to 1,1.' liiMl thciv iM> lon-'T M rcM^onahlo .loiibt tliat the 

 .liflVi-.'iiti.-iN wii.-it.'v.'i' lliov m;iv lu'. iv^| )..nHble for the 

 <li>lin.'tiv.'m'.^> of til.' iinit-cliam.'trr^. reside m 



