August 28, 1914] 



SCIENCE 



299 



within itself the whole range of diversity 

 which living things present. I do not sug- 

 gest that we should come to a judgment as 

 to what is or is not probable in these re- 

 spects. As I have said already, this is no 

 time for devising theories of evolution, and 

 I propound none. But as we have got to 

 recognize that there has been an evolution, 

 that somehow or other the forms of life 

 have arisen from fewer forms, we may as 

 well see whether we are limited to the old 

 view that evolutionary progress is from the 

 simple to the complex, and whether after 

 all it is conceivable that the process was 

 the other way about. "When the facts of 

 genetic discovery become familiarly known 

 to biologists, and cease to be the preoccupa- 

 tion of a few, as they still are, many and 

 long discussions must inevitably arise on 

 the question, and I offer these remarks to 

 prepare the ground. I ask you simply to 

 open your minds to this possibility. It in- 

 volves a certain effort. "We have to reverse 

 our habitual modes of thought. At first it 

 may seem rank absurdity to suppose that 

 the primordial form or forms of protoplasm 

 could have contained complexity enough to 

 produce the divers types of life. But is it 

 easier to imagine that these powers could 

 have been conveyed by extrinsic additions? 

 Of what nature could these additions be? 

 Additions of material can not surely be in 

 question. "We are told that salts of iron in 

 the soil may turn a pink hydrangea blue. 

 The iron can not be passed on to the next 

 generation. How can the iron multiply 

 itself? The power to assimilate the iron 

 is all that can be transmitted. A disease- 

 producing organism like the pebrine of silk- 

 worms can in a very few cases be passed 

 on through the germ-cells. Such an organ- 

 ism can multiply and can produce its char- 

 acteristic effects in the next generation. 

 But it does not become part of the invaded 

 host, and we can not conceive it taking part 



in the geometrically ordered processes of 

 segregation. These illustrations may seem 

 too gross; but what refinement will meet 

 the requirements of the problem, that the 

 thing introduced must be, as the living 

 organism itself is, capable of multiplica- 

 tion and of subordinating itself in a defi- 

 nite system of segregation? That which 

 is conferred in variation must rather itself 

 be a change, not of material, but of arrange- 

 ment, or of motion. The invocation of 

 additions extrinsic to the organism does not 

 seriously help us to imagine how the power 

 to change can be conferred, and if it proves 

 that hope in that direction must be aban- 

 doned, I think we lose very little. By the 

 re-arrangement of a very moderate number 

 of things we soon reach a number of possi- 

 bilities practically infinite. 



That primordial life may have been of 

 small dimensions need not disturb us. 

 Quantity is of no account in these consid- 

 erations. Shakespeare once existed as a 

 speck of protoplasm not so big as a small 

 pin's head. To this nothing was added 

 that would not equally well have served to 

 build up a baboon or a rat. Let us con- 

 sider how far we can get by the process of 

 removal of what we call ' ' epistatic ' ' factors, 

 in other words those that control, mask, or 

 suppress underlying powers and faculties. 

 I have spoken of the vast range of colors 

 exhibited by modern sweet peas. There is 

 no question that these have been derived 

 from the one wild bi-color form by a proc- 

 ess of successive removals. When the vast 

 range of form, size and flavor to be found 

 among the cultivated apples is considered 

 it seems difficult to suppose that all this 

 variety is hidden in the wild crab-apple. 

 I can not positively assert that this is so, 

 but I think all familiar with Mendelian 

 analysis would agree with me that it is 

 probable, and that the wild crab contains 

 presumably inhibiting elements which the 



