No. 613] SHORTER ARTICLES, DISCUSSIONS, RE 1 r lE W8 6 i 



though unproved. But I is not a member of that group, but is 

 only linked to it, being, as we may say, in the same chromosome. 

 The work that Nabours has done makes that certain, and disposes 

 also, by the way, of the likelihood that non-disjunction explains 

 the similar case in the first paper (Bridges, '16). 



Nabours has made a sort of mystery of the character called G 

 in his first paper, but now called 6, which, he says, is "only allelo- 

 morphic to its absence." Ignoring the philosophy of this state- 

 ment, he has shown that 6 mendelizes independently of the other 

 characters. He suggests that such determiners may be of fre- 

 quent occurrence. He has shown that by substituting (iivek 

 letters for English letters the formulae will work out as well as 

 they did before, and has naively applied the method to the case 

 of comb inheritance in poultry. His difficulty is simply caused, 

 and Bellamy has pointed out its solution : 



It need only be assumed that the determiner is borne by some other 



In Drosophila some four or five years ago, the determiner for 

 bent wings was the only one known for the fourth chromosome 

 group. If at that time we had known only one other set of char- 

 acters in Drosophila, viz., that of the white-eosin group, the situ- 

 ation would have been parallel to the one described by Nabours. 

 We might speak of a half dozen or so of "characters allelo- 

 morphic to each other," and of one, bent, " allelomorphic only 

 to its absence." Later on, when we found other characters 

 whose determiners were located in the fourth chromosome, we 

 should modify our theory. Nabours 's industry in his research 

 makes me feel safe in prophesying that he will yet discover some- 

 thing linked to 0. 



He says parenthetically that two other characters "apparently 

 of the nature of $" have been discovered. It is important to 

 find out their linkage relations and we shall wait eagerly to hear 

 of them. In the meantime we must conclude that he has discov- 

 ered the beginning of at least two chromosome groups. 



BIBLIOGRAPHY. 



