256 APPENDIX III— LETTERS PUBLISHED IN NATURE. 



In Nature for ( October 22, 1896, page 605, mention is made of a dis- 

 cussion on \eo-Lamarekism at the British Association. In opening 

 the discussion, Prof. Lloyd Morgan referred to the importance of 

 noting the bearing of certain cases that may be considered as crucial, 

 or as nearlv crucial as any that we are at present able to obtain, on 

 the process by which specific instincts are built up. As illustrating 

 this class of cases, he refers to the drinking instinct in newly hatched 

 chickens, where the instinctive response begins at the point where the 

 teaching of the parent bird would naturally be inadequate. 



The question I wish to raise is whether such observations as this 

 can do more than justify the conclusion that life-saving instincts are 

 strengthened and established by natural selection. Are they suffi- 

 cient to show that all permanently inheritable specific characters are 

 wholly due to natural selection, or even that natural selection is 

 always one of the factors by which any and every permanent character 

 has been built up ? It seems to me that there are large classes of facts, 

 some of which may be found in almost every species we examine, 

 which throw doubt upon there being any such inseparable connection 

 between natural selection and the inheritance of characters. 



1. Right-handedness and Left-handedness. 



The majority of the human species inherit right-handedness. Does 

 this prove that right-handedness is better for the race than left- 

 handedness? The shells of most snails are coiled in a way that is 

 called dextral ; but some groups of species are as constantly sinistral 

 as most groups are dextral ; and of the dextral groups there are cer- 

 tain species that are persistently sinistral; others that are nearly 

 equally divided between dextral and sinistral forms. Is it necessary 

 to believe that for each species that is usually either dextral or sinistral 

 there is some vital necessity that would exterminate, or even dimin- 

 ish, the species if the character was reversed? A similar class of 

 cases is found amongst the different species of flatfish. One species 

 persistently lies on the right side, another on the left, and I think it is 

 Mr. Cunningham who has told the readers of Nature that there are 

 some species in which both forms may occur. In each of these classes 

 of cases I am unable to conceive of any advantage gained by the 

 species that would not be equally gained if the character under dis- 

 cussion was reversed. // the adaptation to the environment of a flat- 

 fish that now lies upon the right side would be equally good in case all the 

 individuals of the species lay upon the left side, then {if I rightly under- 

 stand the meaning of the terms) , natural selection can not be the cause of 

 its lying on the right side rather than the left, neither can this character of 



