42 Myr. J.W. Tutt on 7. lustortata and T. crepuscularia. 
similarity of the single specimen of 7. bistortata that is 
exhibited and that emerged as the representative of 
a third brood on August 17th, 1896, to a small 7. 
erepuscularia, though the rest of the pupz of the brood 
that went over the winter emerged as typical 7’. bistortata 
melSOT.: 
Mr. Bacot has given me the following interesting 
information on the early stages :— 
(1) The ova of 7. bistortata are considerably larger than 
those of 7. erepuscularia. The ova of all the hybrids 
examined approach more nearly in size to those of 7. 
crepuscularta, mM some cases being somewhat smaller. Dr. 
Riding gives the relative sizes of the ova as—T. bistortata 
(Ist brood): 7. bistortata (2nd brood): TZ. crepuscularia : 
ovum of hybrids :: 4°25: 3°75: 3:5: 3. 
(2) The hybrid larvee feed up more rapidly than those 
of either parent species. 
(3) There is a slight tendency for the hybrid larve to 
follow the larval form of the female parent; at the 
same time, there is a much more strongly marked 
tendency for the larvee of all the crosses to follow the larva 
of 7. bistortata, 2.e., that whilst the larvee of all the crosses 
are very close to those of 7. bistortata, as regards the dark 
united A, a larger proportion of the cross 2 7. crepuscularia 
x ¢T. bistortata tends to have a distinct gap at the apex 
than is the case with the reciprocal cross. 
(4) In the batches of inbred hybrid crosses that 
produced fertile eggs, a certain number failed to hatch, an 
event quite without parallel im the eggs of the first crosses. 
[Dr. Riding also notes that in the inbred hybrid crossings 
that he obtained, which produced fertile eggs, only some 
were fertile. | 
(5) The larva of the inbred hybrids inclined rather to 
those of 7’. crepuscularia than to T. bistortata, although a 
few larvee had theAmark united as in the larva of T. 
bistortata. 
