R K. Nabours 145 



Any two of these letters placed side by side will represent the hetero- 

 zygous, or hybrid zygote, or individual, produced by the union of the 

 homozygous gametes represented by the respective letters. 



Early in September, 1908, specimens of the general appearance of 

 texanus, leuconotus, leucothorax, and punctofemorata (Plate VI, figs. 

 1 — 4), were obtained in the vicinity of Houston, Texas. At that time 

 nothing whatever was known of their composition, and the females were 

 not virgin. All the forms were placed in a tin bucket and ttiken to 

 Chicago. One specimen, a male of the appearance of leuconotus 

 (Plate VI, fig. 2), two specimens, females, of the appearance of leuco- 

 thorax (Plate VI, fig. 3), and several males and females of texanus 

 and punctofemorata survived (Plate VI, figs. 1 and 4). 



Experiment I. On September 12th, the male of the appearance 

 of leuconotus was mated to the two females of the appearance of 

 leucothorax (Table I, parents). The progeny which hatched in 

 November and December grew slowly and after great mortality 

 matured in the following March, and showed in F^ five types as 

 follows : 5 of the appearance of leuconotus, 6 leucothorax, 6 inter- 

 mediate between leuconotus and leucothorax, 12 texanus, and 3 puncto- 

 femorata (Table I, F^). The inbreeding of these F^ types, each type 

 to itself, in the F^^ generation was as follows : two pairs of the leuconotus 

 type were mated in separate cages and gave Fo progeny as follows : in 

 cage (a) 34 leuconotus {B) and texanus-leuconotus {AB) : 14 texanus 

 (A), and in cage (6) 24 leuconotus (B) and texanus-leuconotus (AB) : 



7 texanus (A)] the total numbers for the two Ciiges being 59 leuconotus 

 (B) and texanus-leuconotus (AB) : 21 texanus (A), with the expectation 

 of 60 : 20, respectively. The F^ leuconotus-leucothorax (i^C) hetero- 

 zygotes were inbred, as a group culture, and gave in F^, 66 leuconotus; 

 136 leuconotus-leucothorax (BC) : 58 leucothorax, the expectation being 

 65 : 130 : 65, respectively. The ^i leucothorax type inbred, three pairs 

 in separate cages, gave progeny in F^ as follows : in cage (a) 43 leuco- 

 thorax and texanus-leucothorax (AC) : 7 texanus (A); in cage (b) 



8 leucothorax (0) and texanus-leucothorax (AC) : 10 texanus (A); 

 and in cage (c) 66 leucothorax (C) and texanus-leucothorax (AC) : 

 15 texanus (A); the total numbers from the three matings being 

 117 leucothorax (C) and texanus-leucothorax (AC) : 32 texanus (A), 

 with the expectation of 11 1 '75 : 3725, respectively. One of the F^ 

 punctofemorata type, a male, was mated to a texanus female, and they 

 gave in i^j, 9 of the appearance of punctofemorata : 5 texanus. This 

 result shows at least the texanus-punctofemorata (AD) heterozygous 



