252 Variation in the Mealworm, Tenebrio molitor 



much later, but not before the beetle has passed a stage in which its 

 whole body is of a uniform red-brown. 



About crossing experiments between OR x GB, OR x BA, and 

 GB X BA we shall report in a subsequent paper. 



Besides the above deviations in the colour of the T. molitor beetle 

 there may still be recorded one about which I am yet uncertain whether, 

 though in some cases due to a change in conditions, it may not bo 

 caused by a genotypical " Anlage " in other cases. It occurs not rarely 

 that the OR and GB beetles assume not a final black but a final brown 

 hue. This brown, here the last stage of the adult colouring, appears in 

 different shades. Often the light colour is confined to the prothorax, 

 sometimes to the wings alone, and in a minority of cases the whole beetle 

 has a light hue. 



In order to be able to state the amount of difference between the 

 normally coloured beetle and the light coloured individuals one should 

 observe them both in a glass dish on a coal black background ; beetles 

 then showing a clear difference of colour, may scarcely exhibit this when 

 examined on a white ground. Among 10,661 beetles examined, which 

 were kept for eight days in the incubator during the coloration process, 

 there were 165 whose colour on a white ground (i.e. under unfavourable 

 conditions for comparison) displayed a conspicuous light brown tint, 

 i.e. about 15 per mill. 



An F-y generation of these beetles was kept. The same selective 

 process was applied to it in behal^of an F^, and later again of an F^ and 

 Fi generation. In this way I hoped to isolate a strain which, as to the 

 final stage of the coloration, differed genotypically from the more general 

 type whose adult colour is nearly black. These selective experiments 

 are not yet finished, and I will refrain here from any anticipatory judg- 

 ment about the possible result. 



As far as my experience goes it is beyond any doubt that an abnormal 

 course of the colouring process may be brought about either by disturb- 

 ances in the development of the beetle during the pupal stage, or by 

 other outward circumstances the nature of which I am not yet able 

 to define. 



7. Hereditary and N on- Hereditary Anomalies. 



The cardinal point of these investigations lay in the search for devia- 

 tions from the normal type in order to study them with a view to their 

 behaviour in heredity. In this I have been but slightly influenced by 



