H. Onslow, 127 



These figures leave no possible doubt of the recessive behaviour of 

 the melanic variety when mated with grossulariata. It will be observed 

 that in both melanics and non-melanics of the last table the cTc/ are 

 considerably in excess of the $ $ . These numbers may be compared with 

 those given in the Table on p. 135, where attention is called to this sex 

 ratio. 



Var. hazeleighcnsis, and intermediates. 



The normal variety oivarleyata is shown in Plate XIX. The (quantity 

 of white round the base of the wings varies from the amount seen in 

 Fig. 1, where it includes the discoidal spot, to the amount seen in Fig. 10, 

 where practically all the white is gone from the fore wings. It has 

 already been mentioned that the F^ generation, from varleyata x grossu- 

 lariata, often gives individuals which are darker than the normal type 

 form. Fig. 5 shows a typical grossidariata ; Figs. 6, 11, 12 are forms with 

 increasing amounts of black pigment. The blackest individual. Fig. 12, 

 corresponds to var. hazeleighensis, and has fore wings all black, or with 

 a few flecks of white. It will be noticed that its hind wings are not 

 very different from those of the type insect Fig. 5, although the fore 

 wings have actually more black than some examples of varleyata. 



In order to gain an idea of the amount of black that was present 

 in the intermediate varieties, an attempt was made to measure the 

 extent of the black areas in the different individuals, and to express 

 this as a percentage of the total area of the wing. The following pro- 

 cedure was found to give very satisfactory results. The insects are 

 pinned to a board in such a position that when viewed through a camera 

 lucida\ a magnification of two diameters is obtained, A drawing is then 

 made of the outline of the wing and of the black pattern. An accurate 

 measurement of the different areas can then be made by means of a 

 planimeter, the maximum error of which is not more than 1 per cent. 



This method could with advantage be extended so as to apply to 

 other cases, where the genetics of pattern factors are being studied, 

 such as many problems in the inheritance of coat colour, involving more 

 or less elaborate patterns upon white or coloured grounds. This might 

 be done at least in all cases where the skin could be spread out flat, 

 and would surely be preferable to assigning the specimens to arbitrary 

 grades by means of the eye. 



- A suitable instrument is sold by Lechertier Barbe, 95 Jermyn Street, S.W. A set of 

 lenses is supplied with the instrument, which are said to enable the operator to make 

 enlargements or reductions to any desired size. 



