A THEORY OF HEREDITY. 225 



When each sperm cell or oocyte of the first filial generation is a 

 hybrid of mother and father, it gives rise to ova or spermatozoa by 

 reduction division with a loss of one-half of its chromosomes, thus becom- 

 ing like mother or father. Then it unites with a like or unlike cell of the 

 opposite sex (ovum or sperm) and reproduces type according to Mendel's 

 laws. This applies when the cross of two opposite extremes in one 

 character takes place, as when blue eyes and brown eyes (Davenport), 

 long and broad head or long and wide face are crossed (Boas), but not 

 when this is the case with the two opposite extremes of other characters, 

 such as ear length in rabbits. Blending ultimately manifests itself 

 even in the most diverse characters that at first exhibit Mendel's law in 

 all cross-mating. Castle has shown that relocated crossing for many 

 generations alters apparently pure characters, so that black hair becomes 

 contaminated with white and white with black, and although continual 

 crossing has not been carried on further than this, there is reason to 

 believe that ultimately the extremes will produce a perfect blend. 



In any cross of extremes the chromosomes or side chains of the germ 

 cells are in unstable equilibrium. In the next generation there is a 

 rearrangement of the chromosomes in all possible combinations, giving 

 a ratio of apparent dominant to recessive, of 3 to 1, 9 to 1, or 27 to 

 1, with one character, two characters, or three characters respectively. 

 Continual crossing inter se enables the side chains or chromosomes to 

 become accustomed to those of the opposite nature by continued union 

 and disunion in the sex cells; the opposite qualities become reconciled, 

 as it were, and blend slightly. This blend becomes more and more 

 perfect and complete as generation succeeds generation. 



It is to be supposed that when two distinct types of men come together 

 and intermarry, there will be a conformity to Mendel's laws more or less 

 complete for each character, depending upon the distinctness of the 

 types ; then a gradual alteration of each type in the direction of the other 

 takes place until finally, if time and other circumstances permit, there 

 is a perfected blend of the two. This has probably occurred in Austra- 

 lia, Tasmania, and other isolated regions, and is now going on in nearly 

 all parts of the world. 



Prehistoric Europe, Asia, and Africa were overrun by hordes of little 

 people now generally Icnown as Iberians, who settled the British Isles, 

 the Atlantic coast and the Mediterranean basin almost to the exclusion 

 of all others. The Iberians were short, slender, delicately molded in- 

 dividuals with coal-1}lack hair and eyes, a tan complexion and a very 

 long, narrow, high head represented to-day by the most characteristic 

 Spanish type. (Pis. I, VI, etc.) This stock was superseded in early 

 historic times by the Celt or Gaul who conquered or peacefully infiltrated 

 the region of central Europe and the British Isles, but did not drive 

 out or exterminate the little dark men of prehistory. The Celt (Pis. II 



