470 Mr. W. C. D. Whetkam [May 3, 



These phenomena are explained if we assume that the germ cells 

 of the pea bear either the character " tall " (D = Dominant) or the 

 character " dwarf " (R = Eecessive). By the chance conjunctions 

 of opposite cells we then get the pedigree, 



DD = RR 

 A pure-bred dominant crossed I 

 with a pure-bred recessive gives | 

 offspring all of the mixed type, | | 

 DR, which self-fertilized give, DR = DR 

 from a large number of seed, I 

 one quarter DD, one quarter RR, 

 and half DR, I j j j 



DD DR DR RR 



which agrees with the experimental relations we have described. 



Similar results, often complicated it is true with the Hnkage of 

 qualities and in other ways, have l)een found for many characters of 

 plants and animals. In mankind also the phenomena of the segre- 

 gation of unit characters appear. Thus eye-colour is a Mendelian 

 character, lJro^vn l»eing dominant, and lilue or grey recessive. Brown 

 eyes can only be transmitted by those who themselves possess them, 

 while two blue-eyed parents never have a l)rown-eyed child (SUde 

 No 17). ^Many diseases and physical defects also show Mendelian 

 descent. Instances are the shortening of fingers, known as brachy- 

 dactyly (Shde No. 18), and cataract (Slide No. 19). 



Now, the importance of these MendeUan relations hes in the fact 

 that they enable us to predict the probable result, as far as these 

 quahties are concerned, of any given marriage, and, in large families 

 to foretell almost the exact proportion in which a character may be 

 looked for in the descendants. When more of these phenomena have 

 been traced, and are generally understood, they cannot but have a 

 profound social significance. 



The facts we have passed in review force on our minds the con- 

 ception of the nation as composed of families as the true social unit. 

 Each family with its inliorn qualities, changing from generation to 

 generation in accordance with the wisdom or folly of its mamages, 

 Ijut at any given time of definite value, is an asset to or a charge on 

 the nation of which it forms part. Environment may give those 

 qualities a fair chance or condemn them to useless steriUty ; hence 

 the importance of a good environment, towards which, indeed, all 

 our efforts have hitherto been directed. But it seems that acquired 

 characters are not inlierited, and so environment cannot create inborn 

 quahties, though a race of good inborn aptitudes will inevitably create 

 ultimately a good environment. 



How far is the more fundamental and more important factor of 

 the inljorn character of the race under our own control ? Can we 



