64 JOUKNAL OF THE MiTCHELL SOCIETY \_AugUSt 



in previous epochs. This remarkably intense interest in the 

 facts of structure, resulting in evolutionary interpretations in 

 the shape of race-histories or phylogenies, was the most dom- 

 inant force at work throughout the whole range of biology until 

 about 1890. In zoology especially most of the strong, keen 

 minds were active in such investigations. 



Science consists primarily of demonstrable facts, arranged in 

 generalizations of more and more comprehensive scope, in such 

 wise as to expose the time relation between the antecedent 

 facts or cause and the sequent facts or effect. These generaliza- 

 tions glued together with theory make up in any age the con- 

 temporaneous body of science, which the members of that gen- 

 eration see in the mind's eye when they piece together all they 

 know or have some reason to believe in concerning material 

 phenomena. Naturally as generalizations widen, and theories are 

 verified, disproved, or changed, our mental picture of that 

 stately building of science (to borrow a favorite Germanism) 

 changes too. And so the picture drawn by those of a preceding 

 generation may look in many particulars strangely unlike that 

 which we see today, but if they were and we are good workers, 

 the next generation will see in the two pictures beneath the 

 superficial dissimilarities much the same basic framework of 

 lines. It is this well known use of theory which exposes us 

 sometimes to the dashing onset of the clever tongued and light 

 minded, who allege that we are no better than others, that we 

 too muddle up fact and fancy. Peace to the satirist and thanks, 

 if only he have humor and not mere impudence ! We do 

 not muddle, or at any rate (for we are only men) we try not to 

 muddle fact and fancy. Nevertheless we certainly eke out fact 

 with fancy, in the shape of hypotheses. But these we must 

 continually try out in the daily round of experience. Do obser- 

 vation and experiment confirm the fancy? we ask. And then 

 we find, or others find, that most of the hypotheses prove untrue 

 and are to be discarded. Some quickly prove true, and if for 

 these we continue to use the term "theory," we do so from habit. 

 So it is with the "cell theory," long ago demonstrated to be 

 fact. Others deal with phenomena of such a kind that we can 



