212 The Inheritance of Wing Colour in Lepidoptera 



the other. The colour slips F are then placed in the grooves until an 

 equivalence of colour has been obtained in both fields of view. The 

 coloured object may of course be placed indifferently on either side 

 without affecting the result. In making the measurements here re- 

 corded a low power lens B, magnifying about three diameters, was 



A 



Fig. 1. The "Tintometer " arranged for reading the colour of an insect, 



A. Eye-piece. B. Tube. C. Compressed plaster of Paris background. D. Lens. 

 E. Cardboard diaphragms. F. Standard coloured glasses. G. Slots to hold glasses. 



placed between the insect and one aperture. A variety of different 

 sized diaphragms were also cut in black card. These were placed in the 

 metal slots E in order to mask the black markings of the insect, which 

 might otherwise have interfered with the colour determinations by 

 introducing a contrast effect. A second diaphragm of the same size 

 was placed on the opposite side from the insect in order to equalise the 

 two beams of light. 



The colour scale. 



The colours of the glass slips used are yellow, red and blue. The 

 scale consists of twenty units, each divided into ten parts, every one of 

 these parts being again divided into a further ten fractions. It is 

 however only with the paler colours that an increment of 0*01-0'05 

 becomes appreciable. These three colours can be combined to form any 

 other colour required. Thus, one unit of red + one unit of yellow = one 



