II. 



ON HEREDITY. 



WITH your permission I wish to bring before you to-day my 

 views on a problem of general biological interest the problem of 

 heredity. 



Heredity is the process which renders possible that persistence 

 of organic beings throughout successive generations, which is 

 generally thought to be so well understood and to need no special 

 explanation. Nevertheless our minds cannot fail to be much per- 

 plexed by the multiplicity of its manifestations, and to be greatly 

 puzzled as to its real nature. A celebrated German physiologist 

 says 1 , 'Although many hands have at all times endeavoured to 

 break the seal which hides the theory of heredity from our view, 

 the results achieved have been but small ; and we are in a certain 

 degree justified in looking with little hope upon new efforts under- 

 taken in this direction. We must nevertheless endeavour from 

 time to time to ascertain how far we have advanced towards a 

 complete explanation.' 



Such a course is in every way advisable, for we are not dealing 

 with phenomena which from their very nature are incomprehensible 

 by man. The great complexity of the subject has alone rendered it 

 hitherto insuperable, but in the province of heredity we certainly 

 have not reached the limits of attainable knowledge. 



From this point of view heredity bears some resemblance to cer- 

 tain anatomical and physiological problems, e. g. the structure and 

 function of the human brain. Its structure with so many millions 

 of nerve-fibres and nerve-cells is of such extraordinary complexity 

 that we might well despair of ever completely understanding it. 

 Each fibre is nevertheless distinct in itself, while its connection 

 with the nearest nerve-cell can be frequently traced, and the function 

 of many groups of cell elements is already known. But it would 

 seem to be impossible to unravel the excessively complex network 

 1 Victor Hensen in his ' Physiologic der Zeugung,' Leipzig, 1881, p. 216. 



