22 THE CASE AGAINST EVOLUTION 



pair, but if one or more chromosomes be added to, or sub- 

 tracted from, this balanced triploid complex, the mutant is 

 termed an unbalanced triploid. When all the chromosomes 

 of the normal diploid complex are uniformly doubled, we have 

 a balanced tetraploid race. The subtraction or addition of one 

 or more chromosomes in the case of a balanced tetraploid 

 complex renders it an unbalanced tetraploid mutant. The 

 retention in somatic cells of the haploid niunber of chromo- 

 somes characteristic of gametes and gametophytes gives a 

 balanced haploid mutant, from which hitherto no unbalanced 

 haploids have been obtained. The normal diploid type and 

 the balanced tetraploid type are said to constitute an even 

 balance, while balanced triploids and haploids constitute an 

 odd balance. The odd balances and all the unbalanced mu- 

 tants are largely sterile. Thus, for example, more than 80% 

 of the pollen of the haploid mutant is bad. "The normal 

 Jimson Weed," says Blakeslee, "is diploid (2n) with a total 

 of 24 chromosomes in somatic cells. In previous papers the 

 finding of tetraploids(4n) with 48 chromosomes and triploids 

 (3n) with 36 was reported, as well as unbalanced mutants with 

 25 chromosomes represented by the formula (2n+l). The 

 finding of two haploid or In plants, which we are now able 

 to report, adds a new chromosomal type to the balanced series 

 of mutants in Datura. This series now stands: In, 2n, 3n, 4n. 

 Since a series of unbalanced mutants has been obtained from 

 each of the other balanced types by the addition or sub- 

 traction of one or more chromosomes, it is possible that a 

 similar series of unbalanced mutants may be obtainable from 

 our new haploid plants, despite the great unbalance which 

 would thereby result." (Science, June 16, 1923, p. 646.) The 

 haploid mutant, of which Blakeslee speaks, has, of course, 12 

 unpaired chromosomes in its somatic cells. 



The balanced triploid is, like the haploid mutant, largely 

 sterile, and is only obtainable by crossing the tetraploid race 

 with the normal diploid plant. Since, then, the product of 

 the cross of the diploid and tetraploid races is sterile, the 



