72 ORGANIC EVOLUTION — THE FACTORS 



differentiated, specialized, and arranged in a definite 

 order, so it is possible or probable are the biaphors of 

 a cell differentiated, specialized, and arranged in a 

 definite order; and as all differences between multi- 

 cellular organisms are due to differences in the differ- 

 entiation, specialization, arrangement, and number of 

 their cells, so all differences between cells are possibly or 

 probably due to differences in the differentiation, special- 

 ization, arrangement, and number of their biaphors ; 

 and as higher multicellular organisms are more hetero- 

 geneous and complex as regards the nature and arrange- 

 ment of their cells than lower multicellular organisms, 

 so higher unicellular organisms are possibly or probably 

 more heterogeneous and complex as regards the nature 

 and arrangement of their biaphors than lower unicellular 

 organisms ; from which, if true, it follows as a corollary, 

 that higher unicellular organisms are less cajDable of 

 transmitting acquired variations than lower unicellular 

 organisms, a deduction which is in accordance with the 

 facts, so far as they have been observed ; for while 

 experiments have demonstrated that the microbes (in. 

 every case extremely low organisms) of several diseases 

 are modifiable by cultivation in changed media, there is 

 nothing to prove that higher unicellular organisms such 

 as the amoeba are as easily modifiable. As regards the 

 small-pox microbe, since it is so readily modifiable by 

 removal to a different medium, — i. c. the calf's body, — it 

 must, if there is any truth in this hypothesis, be a very 

 low organism — low as regards the number, arrangement, 

 differentiation, and specialization of its biaphors — a view 

 which is borne out by the fact, that it is so minute that 

 it has never been seen, notwithstanding the exceptional 

 facilities that the limpid vaccine lymph affords fbr 

 microscopic investigation ; possibly it is so minute as to 

 be quite beyond tlie powers of devisable microscopes, in 

 which case it will never be discovered. 



