J. W. H. Harrison 277 



from its meagre results in fertile eggs the physiological affinity between 

 dilutata and filigrammaria must be exceedingly slight. Contrasting 

 this with what is seen in the parallel autumnata-dilutata cross, where 

 we obtain 100 °/^ fertile ova, and with care an equal number of imagines, 

 we see that the relationship between filigrammaria and dilutata is of a 

 different order from that between autumnata and dilutata. From this 

 it follows immediately that there is a definite physiological difference 

 between autumnata and filigram,rrtaria lifting the latter to a higher 

 evolutionary level than the former — a fact which the perfect fertility of 

 the two forms and their various crosses and back crosses could not have 

 revealed save in the minor disturbance in the ^i hybrid gametogenesis. 

 From the 19 fertile eggs five larvae hatched, and of these four 

 died without feeding; the fifth struggled into its second instar and then 

 followed the majority, their weakness thus confirming the greater diver- 

 gence between dilutata and filigrammaria as compared with that 

 between dilutata and autuTnnata. 



The Pairing between dilutata ? and filigrammaria ^. 



This cross pairing gave absolutely no fertile ova in 1917; a repetition, 

 however, in 1918 has provided me with a brood of which at least 20 °/^ 

 have changed colour and may possibly hatch during the present 

 spring. As far as I have gone, the evidence of the present cross simply 

 reinforces that of the last. 



The Grossing of Cheimatobia boreata $ and O. autumnata </•. 



Owing to the obvious parallelism between the relationship of the 

 genera Cheimatobia and Oporabia and that between Nj/ssia and Lycia, 

 it occurred to me that hybridity between the first named generic pair 

 might be feasible. Moreover, I considered that if this were so, further 

 information might be gained as to the inheritance of apterousness in a 

 group far removed from the well worked Bistoninae. In pursuit of these 

 possible crosses I caged reciprocal pairs of Cheimatobia boreata and 

 Oporabia autumnata together and awaited events. 



In the cage containing boreata males and autumnata females not a 

 single egg was laid ; nor was the matter greatly improved in the other 

 cage. Instead of tucking neat little cakes of ova in the folds of the 

 muslin the boreata females scattered their eggs irregularly over the 

 cage. This occurrence is generally to be regarded as a certain indica- 

 tion of failure in fertilisation, produced either by oviposition without 

 copulation or by some mechanical hindrance to the passage of sperma- 

 tozoa from the bursa copulatrix through the ductus bursae. In this 



18—2 



