July 17, 1914] 



SCIENCE 



109 



3). The particular composition of the mother 

 can thus be handed on indefinitely from 

 daughter to daughter (see T). 



Only the sex-chromosomes are concerned in 

 this unique maturation and breeding results 

 show that only sex-linked characters are sub- 

 ject to exception in these cases (see 8). 



The Y-eggs (5 per cent.) by the X-sperm 

 give males (217) with no supernumerary 

 chromosomes. These males have received their 

 X-chromosomes from their father and the 

 breeding results (see 4) show that in all sex- 

 linked characters (see 5) they are exact dupli- 

 cates of the father. 



These males will be able neither to produce 

 exceptions (see 6) nor to transmit the power 

 of producing exceptions (see 14) since their 

 chromosome mechanism is that of any ordi- 

 nary male (see 17). 



The XY-eggs (45 per cent.) by the X-sperm 

 will give females (diploid with respect to X 

 (see 11) ) which will, to all appearances, be the 

 type expected from the cross, since they will 

 exhibit characters from either or both parents. 

 But since they contain a supernumerary Y- 

 chromosome they will themselves be able to 

 produce exceptions, and breeding tests showed 

 that half the expected females do in fact pro- 

 duce such exceptions (see 10). 



19. Such non-disjunctional females which 

 are heterozygous for recessive characters, when 

 bred to any male, produce exceptional daugh- 

 ters which are of one type only, namely, hetero- 

 zygous dominants. This fact shows that the 

 rpon-disjunction occurs at the reduction di- 

 vision, for if at the reduction division the X- 

 chromosomes separated the egg would receive 

 either the dominant bearing chromosome or 

 the recessive bearing chromosome. After the 

 following equational division of the chromo- 

 somes two nice chromosomes would be pro- 

 duced, both dominant or both recessive bear- 

 ing. If non-disjunction occurred at this stage 

 (2d polar body) exceptional daughters pure 

 dominant or pure recessive would appear. 

 Since females of this type do not appear, we 

 must conclude that the non-disjunction occurs 

 normally at the reduction division and not at 

 the equation division. 



The XF-eggs (45 per cent.) by F-sperm give 

 males (XF^male) with a supernumerary F- 

 chromosome. Since these males receive their 

 F-chromosomes from their mother they will 

 be of the expected classes of sons (see 12). In 

 the spermatogenesis of such males the extra F 

 may go either with X or with the other F and 

 these two cases seem to occur with equal fre- 

 quency. The spermatozoa of such a male are 

 then of four types: XF—F—X—FF. When 

 mated to any female only expected offspring 

 could appear (see 12). The types XF and X 

 are female producing. Some of the daughters 

 produced will thus have a supernumerary F 

 and will themselves produce exceptions (see 12 

 and 13). 



Some of the sons of such a cross would pos- 

 sess the power of transmitting non-disjunction 

 as did their father of like composition (see 12 

 and 13). Although the presence of the males 

 having the composition XYY has been proven 

 genetically, their occurrence has not yet been 

 studied cytologically. 



If in a non-disjunctional female F went 

 equally often with either X, then no linkage 

 would be shown between non-disjunction and 

 any sex-linked gene (see 15). 



Likewise the method which would unfail- 

 ingly secure a pure- stock of' any sex-linked 

 gene is utterly useless for a freely segregating 

 F-chromosome (see 16). 



In conclusion, there can he no douht that 

 the complete parallelism between the unique 

 hehavior of the chromosomes and the hehavior 

 of sex-linhed genes and sex in this case means 

 that the sex-linked genes are located -in and 

 home hy the X-chromosomes. 



Calvin B. Bridges 



Columbia University 



hot water treatment for cotton anthracnose 

 During the past three months we have been 

 making a study of the effect of hot water at 

 different temperatures on the anthracnose 

 fungus and cotton seed. The results are very 

 interesting and seem to have an important 

 bearing on the control of the disease. Cotton 

 anthracnose is known to be carried in the 

 seed. The fungus penetrates the seed coats 



