150 Cross-breeding of Tivo Races of the Moth Acidalia virgularia. 



We noticed also that the larvse were very variable, and it is not impossible 

 that an analysis of their variation might yield some results of value. 



As a final impression, we would suggest that our failure to find Mendelian 

 inheritance at work was due mainly to our bringing together two compara- 

 tively remote geographical races (as with Messrs. Warburg and Bacot's 

 Lasiocampa meridioncdis x callunce) and that we, personally, noAv only expect 

 to find segregation in the case of crosses of two forms occurring together (like 

 the two forms of Triphcena comes or those of Xantlwrlwe ferrugoto), where 

 a long course of natural selection has presumably eliminated the inter- 

 mediates. We pointed out in the introduction that just such intermediates of 

 Acidalia virgularia as were produced artificially by crossing our specimens 

 from London and Hyeres (localities where they are apparently quite 

 unknown in a wild state) do occur in a state of nature in other parts of its 

 geographical range. 



A few pairings which occurred in generation Fi produced ova which have 

 been handed to Mr. W. Bateson in the hope that he may be able to follow up 

 our researches in the species. Unfortunately both the pure strains have been 

 lost, but possibly Mr. Bateson will be able to extract them, by selective 

 pairing, from the new hybrids, which we labelled Mxi and m xi. 



