240 The Inheritance of Wing Colour in Lepidoptera 



the curves between the two classes is so clearly defined, and occurs so 

 often in the same position in various families, that there can be no doubt 

 it is significant and proves that even in the DR x RR families segre- 

 gation really takes place. 



A certain number of variations, which appeared during the course of 

 the experiments, are described and figured. Very little is at present 

 known of their genetics, but a table is given, enabling all details of their 

 occurrence in the curves showing the distribution of the colour-values 

 to be easily found. Further experiments are being conducted with 

 var. varleyata as well as certain other varieties. 



Special attention has been paid to the manner in which the pigments 

 are deposited within the scale, and to the exact modifications which are 

 the cause of certain varieties. Variations in the position and concen- 

 tration of the melanic pigment are, for instance, the only factors which 

 govern the difference between the two suffused varieties iochalca and 

 nigrosparsata. 



A microscopical examination of the scales, both in situ and when 

 sectioned, shows that in the deepest colours the yellow pigment is 

 diffused throughout the chitinous walls of the scales, without the 

 formation of any granules. The intensity of the colour must therefore 

 be determined, either by variations in the concentration, or by a change 

 in the nature and consequently in the colour of the pigment itself. If 

 the yellow variations are simply due to differences in the concentration 

 of the colouring matter, suitable factors capable of controlling such 

 quantitative changes must be formulated. 



The chemical nature of the white and yellow pigments has been left 

 for the subject of a further investigation. 



\Note added on July 19th, 1919.] Since the above was written, the 

 1918 broods have emerged. On the whole the additional evidence from 

 these insects (over 700) confirms the previous conclusions, but one fresh 

 point of interest has been observed. In all the families previous to 

 1918 (except Dr Doncaster's) no lacticolor was used for pairing, lest 

 this factor should complicate the case. In 1918 however the following 

 pairings were made : 



18 V lacticolor $ [0*8 : 0*8] x lutea ^ [3-2 : 2-5] 



18 III lutea % [3-7 : 4-4] x lacticolor ^ [0*9 : 0-8] 



18 V lutea $ [3-2 : 3'5] x lacticolor ^ [0-8 : 0-8] 



In families 18 III and 18 V, the females were all lacticolor, since the 



cf parent was of this variety, and it was noticed that all these $ % were 



