476 MISSES K. FOOT AND E. C. STKOBELL : 



In our preliminary report of this work (Foot and Strobell, '14 c) we 

 discussed the non-linkage of the genital spot and intromittent organ as 

 follows : — 



^' If fjictors which stand for a given character are carried by a definite 

 'chromosome or pair of chromosomes, and the inheritance of the character is 

 due to a special distribution of the factors at mitosis, it would seem logical 

 to expect that the factors of two characters showing a very special mode of 

 distribution (i. e., exclusively male characters) would be contained in the 

 same chromosome, and that this would be indicated by their being linked in 

 the hybrids. We would expect the absence or presence of the genital spot, 

 distinctive of one species, to be associated in inheritance with the type of 

 intromittent organ characteristic of the same species. Even if the extent 

 to which a character appears is dependent upon hypothetical factors outside 

 the chromosomes, v^e would expect these hypothetical factors to act equally 

 on two characters which are so closely associated as to be contained in the same 

 chromosome. We should expect the two characters never to be so entirely 

 dissociated that we find, in the same individual, the absence of spot charac- 

 teristic of one species, associated with the type of intromittent organ 

 distinctive of the other species. Instances of such complete dissociation 



do. however, occur There are instances of association in the inheritance 



of the two characters, the intromittent organ and genital spot, typical of one 

 of the species occurring in the same Fo individual ; but exact classification of 

 the full results shows that the two characters are transmitted quite in- 

 dependently of each other. The intermediates, having a large range of 

 variation, make it possible for many of them to appear to show the two 

 characters in the association that would be in harmony with the chromo- 

 some-hypothesis, but an exact comparison shows two plus and two minus 

 intermediates are quite as frequently associated as are a plus and a 

 minus intermediate." 



These facts are demonstrated in the foregoing tables (3-9), in which the 

 tvpe of inheritance of the genital spot and the length of intromittent organ 

 in each particular insect of the F2 generation are placed side by side. If we 

 examine this evidence in detail, we find that 19 of these 190 F2 males have a 

 oenital spot quite as strong as that of the pure £j\ var'wlarius male, while 

 only 3 of these 19 males have the E. variolarius length of intromittent organ 

 (?'. e., between 85|^ mm. and 106 mm.). 



This evidence of non-linkage is even more clearly shown in those insects 

 which have inherited the servus character (absence of the genital spot). 

 There are 74 of these insects, and oiilt/ 3 have a length of intromittent organ 

 which can be classed with servus, while on the other hand ^ have a length of 

 intromittent organ characteristic of variolarius. The remaining 67, which 

 have the absence of genital spot characteristic of servus, have a mean length 

 ot intromittent organ which shows a stronger influence from variolarius. 

 Tables 3 to 10 further demonstrate that while the influence of variolarius 



