How Darwinism Stands To-Day 385 



very puzzling way differentiation into nerve and muscle, blood 

 and bone, a residue is kept intact and unspecialised to form the 

 beginning of the reproductive organs of the offspring, whence 

 will be launched in due course another organism on a similar 

 voyage of life. The reproductive cells of any organism are the 

 outcome of embryonic cells which did not share in the upbuild- 

 ing of that organism, but continued the germinal tradition un- 

 altered. This is suggested clearly in a diagram slightly modified 

 from one devised by Professor E. B. Wilson. Thus the parent 

 is rather the trustee of the germ-plasm than the producer of the 

 child. In a new sense the child is a chip of the old block. The old 

 question was: Does the hen make the egg, or the egg the 

 hen? The modern answer is that the fertilised egg makes the 

 hen and the eggs thereof. The fact of germinal continuity 

 explains the inertia of the main mass of the inheritance, which 

 is carried on with little change from generation to generation. 

 Similar material to start with; similar conditions in which to 

 develop; therefore like tends to beget like. As Professor Berg- 

 son puts it, "life is like a current passing from germ to germ 

 through the medium of a developed organism." 







As regards Selection 



When we are interpreting the past history of animals, we 

 utilise factors which are seen in operation to-day, just as the 

 geologist does when he is interpreting scenery. It is satisfactory, 

 therefore, that post-Darwinian investigations have demonstrated 

 some modern instances of selection at work. Let us take a simple 

 case. The Italian naturalist Cesnola tethered some green Man- 

 tises with silk thread on green herbage, and found that they 

 escaped the eyes of birds. Similarly, when the brown variety 

 was tethered on withered herbage. But green Mantises on brown 

 herbage and brown Mantises on green herbage were soon picked 

 off. Discriminate selection was at work. 



