JANUABT Ij 1915] 



SCIENCE 



of qualitative and quantitative analysis, 

 synthesis, prediction and verification. 

 More and more clearly it became evident 

 that the phenomena of heredity are mani- 

 festations of definite mechanism in the liv- 

 ing body. Microscopical studies on the 

 germ-cells made known an important part 

 of this mechanism and provided us with 

 a simple mechanical explanation of Men- 

 del's law. And suddenly in the midst of 

 all this, by a kaleidoscopic turn, the 

 fundamental problem of organic evolution 

 crystallizes before our eyes into a new 

 form that seems to turn all our previous 

 conceptions topsy-turvy. 



I will comment briefly on this latest view 

 of evolution, partly because of its inherent 

 interest, but also because it again exem- 

 plifies, as in the ease of embryology, that 

 temptation to wander off into metaphysics 

 {sit venia verho!) which seems so often to 

 be engendered by new and telling discov- 

 eries in science. The fundamental ques- 

 tion which it raises shows an interesting 

 analogy to that encountered in the study of 

 embryology, and may conveniently be ap- 

 proached from this side. 



To judge by its external aspects, individ- 

 ual development, like evolution, would 

 seem to proceed from the simple to the 

 complex ; but is this true when we consider 

 its inner or essential nature? The egg 

 appears to the eye far simpler than the 

 adult; yet genetic experiment seems con- 

 tinually to accumulate evidence that for 

 each independent hereditary trait of the 

 adult the egg contains a corresponding 

 something (we know not what) that grows, 

 divides and is transmitted by cell-division 

 without loss of its specific character and in- 

 dependently of other somethings of like 

 order. Thus arises what I will call the 

 puzzle of the microcosm. Is the appear- 

 ance of simplicity in the egg illusory? Is 

 the hen's egg fundamentally as complex 



as the hen, and is development merely the 

 transformation of one kind of complexity 

 into another? Such is the ultimate ques- 

 tion of ontogeny, which in one form or 

 another has been debated by embryologists 

 for more than two centuries. We still can 

 not answer it. If we attempt to do so, 

 each replies according to the dictates of his 

 individual temperament — that is to say, he 

 resorts to some kind of symbolism; and he 

 still remains free to choose that particular 

 form which he finds most convenient, pro- 

 vided it does not stand in the way of prac- 

 tical efforts to advance our real knowledge 

 through observation and experiment. 

 Those who must have everything reduced 

 to hard and fast formulas will no doubt 

 find this rather disconcerting; but worse is 

 to follow. Genetic research now confronts 

 us with essentially the same question as 

 applied to the evolutionary germ. The 

 puzzle of the microcosm has become that of 

 the macrocosm. Were the primitive forms 

 of life really simpler than their apparently 

 more complex descendants? Has organic 

 evolution been from the simple to the com- 

 plex, or only from one kind of complexity 

 to another? May it even have been from 

 the complex to the simple by successive 

 losses of inhibiting factors which, as they 

 disappear, set free qualities previously 

 held in check? The last of these is the 

 startling question that the president of the 

 British Association propounds in his re- 

 cent brilliant address at Melbourne, asking 

 us seriously to open our minds to the in- 

 quiry: "Whether evolution can at all rea- 

 sonably be represented as an unpacking of 

 an original complex which contained 

 within itself the whole range of complexity 

 which living things exhibit?" This con- 

 ception, manifestly, is nearly akin to the 

 theory of pangenesis and individual devel- 

 opment, as elaborated especially by De 

 Vries and by Weismann. It inevitably re- 



