NATURAL SELECTION 89 



many unpromising articles of diet, without resorting to the 

 ultimate test. Sir Joseph Hooker describes the tortures that 

 he found the members of a savage tribe undergoing when 

 their ordinary food supply had failed. They had been making 

 experiments on various roots, and frightful pangs of indigestion 

 had resulted. If they had not had their tongues and palates 

 to guide them, matters might have been even worse. Moreover, 

 by the help of taste and sensitiveness of tongue, they would be 

 able to recognise the roots that had caused them such ex- 

 cruciating agony and to avoid them for the future. 



Besides this Mr Herbert Spencer has measured the com- 

 parative sensitiveness of the various parts at the wrong period 

 of life ; has measured them after the attainment of maturity 

 when use and disuse have long continued and have had time to 

 widen congenital differences. The measurements, to be really 

 of value, should be made at birth. 



It remains to be said that he has stated the case for Natural 

 Selection very unfairly. No part of an organism is isolated, as 

 he apparently conceives of it. An animal that can develop great 

 tactile sensitiveness in the tongue will be able to develop it at 

 other places also when it is needed, e.g. in the tips of the fingers. 

 And who will deny that such sensitiveness, brought to perfection 

 at the various points at which he probes and tests his environ- 

 ment, is likely to do him yeoman's service in the struggle for 

 existence, and prove that it has selection-value ? 



IV 



RETROGRESSION 



The evolution of new characters must be accompanied by the import- 



shedding of old, otherwise the complex animal would be over- 

 burdened by an accumulation of out-of-date organs. To drop what is no 

 what is useless or harmful is as important as to add new features jJg eruse - 

 to meet the fresh demands of the environment. It is very 

 natural to complain that the embryo stages only very roughly 



