Hybridising T. bistortata and T. crepuscularia 29 
(2 T. bistortata x 2 TL. ab. delamerensis) x 9 (f T.ab. 
delamerensis x 9 T. bistortata). (2) g (f T. ab. dela- 
merensis X § T. bistortata)x 2 (f T. bistortata x 
T. ab. delamerensis). (8) ¢ (fg T. bistortata x 9 T. ab. 
delamerensis) xX § (f T. bistortata x 2 T. crepuscu- 
laria). (4) £ (¢ T. erepuscularia x 2 T. bistortata) x 
2 (g T. bistoriata x 2 T. crepuscularia). (5) gf (o 
T. bistortata x 2 T. crepuscularia) x 2 (fh T. erepuscu- 
laria x & T. bistortata). Of these different crosses, 
twelve pairings in all were obtained, eleven of which 
gave ova, and yet of these eleven batches only two were 
fertile, both crosses of ~ (f TZ. ab. delamerensis x @ 
T. bistortata) x 2 (gf T. bistortata x @ T. ab. delameren- 
sis). The progeny resulting from these two batches are 
summarised later in this paper (vide, V). Later pairings 
or ¢ (f T. crepuscularia x 2 T. bistortata) x 2 (¢ 
T. bistortata x 2 T. crepuscularia) also proved infertile. 
Dr. Riding, however, obtained four inbred pairings of 
a Cf Tf. bistoriata x 2 T. crepuseularia) x 9 (¢ T. 
bistortata x § T. crepuscularia); one of these produced 
no eggs, another was infertile, the two others were only 
partially fertile. 
V. SECOND GENERATION OF HysBrips.— ¢ ( & ab. dela- 
merensis X 9 bistortata) paired with 2 (gf listortata x 
2 ab. delamerensis).—The parents taken from crossings I], 
and I above respectively. ‘Two batches of eggs, hatched 
June 27th—-30th; 44 imagines examined; emerged be- 
tween August 21st and November 8rd,1897. It is almost 
impossible to classify these. As an approximation the 
following table is appended. 
Sa 12 Most nearly approaching to 7. ab, dela- 
merensis, but with the exception of their 
tendency to unicolorous suffusion very differ- 
ent therefrom. 
2¢ Of a slaty-grey tint, approaching the hue of 
Boarmia gemmaria. 
4d Not unlike pale second-brood specimens of 
T. bistortata. 
2 ¢ Dark fuscous, well-marked, closely resem- 
bling 7’. bistortata from Perthshire. 
Sy) Lag Closely resembling typical Yorkshire 7. 
crepuscularia. 
