On Mendel's Laws. 
2^5 
down and the vessel altogether more manageable; indeed she looks 
trimmed for most weathers.” 
These then are the facts and the hypothesis the relations 
of which to the phenomena of intra-racial heredity have to be 
considered and discussed. The first question to be asked in such 
a discussion, is one that does not seem to have occurred to 
any of Mendel’s followers, viz. : what, exactly, happens if the 
two races A and a are left to themselves to inter-cross freely 
as if they were one race ? It must be remembered that it is only 
the knowledge given by preliminary trials like those carried out 
by Mendel which enables us to state that the races are distinct; 
a man who was merely given a sample of seed from the dominant 
forms occurring after hybridisation had taken place, would con¬ 
clude that they were not so—he would find that A’s crossed 
inter se gave rise to some a’s, though not indeed the reverse, 
and would therefore class the two forms as springing from the 
same stock. Now when A’s and a’s are first inter-crossed we get the 
series of uniform hybrids ; when these are inter-bred we get the 
series of three dominant forms (two hybrids, one pure) to one 
recessive. If all these are again intercrossed at random the 
composition remains unaltered. “ Dominant ” and “ recessive ’’ 
gametes are equally frequent, and consequently conjugation 
of a “dominant” gamete will take place with a “recessive” as 
frequently as with another “ dominant ” gamete. Consider then the 
successive generations of posterity of the dominant forms, starting, 
say, with 300 of which 100 are pure. The 100 pure individuals 
will give rise to dominant forms in the proportion of 50 pure 
to 50 hybrids ; the 200 hybrids may, as segregation takes place, 
be considered as 100 pure dominants and 100 pure recessives, 
the former giving rise to 50 pure dominants and 50 hybrids, the 
latter to 50 hybrid dominants and 50 pure recessives. The 300 
parent dominants, therefore, give rise to offspring in the proportion 
of 250 dominant forms to 50 recessive, i.e., the chance of a 
dominant parent producing a dominant form as offspring is f. 
Now consider these 250 dominants whose parents were dominants 
also, 100 of them being pure and 150 hybrids. The 100 pure 
dominants will give rise as before to 50 pure and 50 hybrid 
forms, the 150 hybrid forms to pure dominants, hybrid dominants 
and pure recessives in the proportion of 37*5 : 75 : 37 * 5 . Five 
hundred dominants whose parents were dominants should therefore 
produce 425 dominant offspring to 75 recessives, i.e., the chance 
