STUDIES ON HADROBRACON BREVICORNIS. 155 



The other produced black males, n adults, 27 pupae; orange 

 males, 30 adults, II pupae; black females, 3 adults, I pupa; 

 orange females, 3 adults, 2 pupae. 



The lethal factor is therefore inherited, there being in this 

 generation 33 crossovers and 97 straights or 25 + per cent, 

 crossovers. 



Although considerable care was taken to preserve the lethal 

 stock it very rapidly died out due to difficulty in getting black- 

 eyed lethal-bearing females, and moreover the total numbers in 

 the fraternities became very small. Only three black-eyed 

 females had offspring in the next generation and these were all 

 males. One produced black, 5 adults, 27 pupae; orange, 20 

 adults, 6 pupae. 



A second produced black. 3 adults, 12 pupae; orange, 15 adults, 

 4 pupae. 



The third produced all adults, 5 black and 9 orange. Although 

 the numbers are very small in this last-mentioned fraternity the 

 failure of any lethal pupae to appear in spite of the presence of 5 

 adult black males is good evidence that the mother originated 

 from a crossover or non-lethal black-bearing egg. 



The total male progeny of all five lethal-bearing females is 

 black, 28 adults, in pupae; orange, 132 adults, 31 pupae; 59 

 crossovers to 243 straights, or 19.5 per cent, crossovers. 



Partial linkage is therefore demonstrated in Hymenoptera. 



During the experiments above recorded a number of the lethal 

 pupae were fixed in Carnoy's fluid for histological examination. 

 Sagittal sections, stained with iron haematoxylin, showed no 

 abnormal growths or defects in any organs. The nature of the 

 lethal effect is therefore unknown. 



