RECENT EXPERIMENTS IN HYBRIDISATION. 199 



of the species. It took rank therefore not as an aberration, 

 but rather as a member of a local race, and with this its 

 behaviour accorded. 1 



4. Aglia ta?i L. cT and do. ab. lugens Stdfs. Like the 

 dark aberration zatima of S. lubricipeda, the dark Aglia tau 

 (called by Standfuss ab. lugens) exists in several degrees of 

 development, from the " ab. fere nigra " of Thierry- Mieg to 

 the " ab. nigerrima" of Bang-Haas. All these different 

 stages of darkening have been obtained by Standfuss from 

 pairings between A. tau and ab. lugens, but no transitional 

 form between the normal A. tau and ab. fere nig7'a has ever 

 been so produced. 



In 1888 Standfuss crossed males of ab. lugens, which had 

 been interbred for two generations, with females of the nor- 

 mal A. tau. In 1889 higens derived from these were em- 

 ployed in the following pairings : lugens $ and tau, ? ; tau 

 c? and lugens ? ; lugens S and do. ? . The specimens of 

 A. tau were in each case of different ancestry from the 

 lugens stock. In 1890 two separate pairings were procured 

 of hcgens S and ? from the third of the above broods, so 

 that the perfect insects emerging in 1891 had both parents 

 and all grandparents of the lugens type. The results of 

 these experiments were curious, and should be studied in the 

 original account (Ha7idbuch, p. 312). Here it may be 

 briefly stated that of the 1889 pairings, the first two (lugens 

 S and tau ? ; tau <$ and lugens ? ) produced about 50 per 

 cent, of each form.' 2 



The third (lugens d and ? ) gave 36 per cent, of tau to 



1 Compare the result of crossing C. dpminula with the local race 

 persona, and see especially Standfuss's figures, Op. cit., Taf. V. Compare 

 also the case of A. betularia and its aberration doubkdayaria {inf., p. 201), 

 which is strikingly analogous with that of P. monacha. 



2 In both of these reciprocal crosses there is a slight preponderance of 

 forms resembling the male parent — in the first instance lugens, in the 

 second tau. This case is fairly analogous with that of the breed of Basset 

 hounds lately investigated by Mr. Francis Galton ("The Average Contribu- 

 tion of each Several Ancestor," etc., Proc. Roy. Soc, 1897, PP- 4 OI "4 I 3)> 

 where the reciprocal crosses of two colour-varieties show a male prepo- 

 tency in the proportion of about six to five {toe. cit., Table I., p. 409). As 

 in the instance of tau and lugens, there are no intermediate forms between 



