xxiT THE PROBLEM OF INSTINCT 507 



exact route of the animal's return known, the assertion 

 so often made, that a special sense of direction is required to 

 explain the facts, cannot be justified. 



A7'c Acquired Characters Inherited^ 



Two very interesting chapters, near the end of the 

 volume, are those entitled *' Are Acquired Characters 

 Inherited," and " Modification and Variation." In the first 

 of these the bearing of the whole of the phenomena of 

 instinct on the vexed c{uestion of inheritance is pointed out, 

 and the conclusion is reached, that although there is little 

 or no satisfactory evidence of the transmission of acquired 

 modifications — that is of habits, or their effects on the 

 organism, as opposed to instincts, yet there are many curious 

 facts which seem to indicate some connection between 

 congenital and acquired characters. What this connec- 

 tion is, the chapter on Modification and Variation attempts 

 to show. 



Modification of the individual by the environment, 

 whether in the direction of structure or of habits, is uni- 

 versal and of considerable amount, and it is almost always, 

 under the actual conditions, a beneficial modification. But 

 every kind of beneficial modification is also being con- 

 stantly effected through variation and natural selection, 

 so that the beautifully perfect adaptations we see in 

 nature are the result of a double process, being partly 

 congenital, partly acquired. Acquired modification thus 

 helps on congenital change by giving time for the necessary 

 variations in many directions to be selected, and we have 

 here another answer to the supposed difficulty as to the 

 necessity of many coincident variations in order to bring 

 about any effective advance of the organism. In one year 

 favourable variations of one kind are selected and indi- 

 vidual modifications in other directions enable them to be 

 utilised : in Professor Lloyd Morgan's words — " Modifi- 

 cation ft.9 siich is not inherited, but is the condition under 

 which congenital variations are favoured and given time 

 to get a hold on the organism, and are thus enabled by de- 

 grees to reach the fully adaptive level." The same result 



