﻿6 the entomologist. 



Concluding Remarks. 

 The outstandiug features of these experiments are as follows: — 



(1) The acceleration in development of the females in the 

 dilutata <y x autumnata 2 cross. 



(2) Only these females showed melanism in this cross. 



(3) Apparently autumnata is more potent in affecting the 

 products. That the hybrid origin of a form has the effect of 

 hastening its development in the pupal stage, in some cases in 

 one sex only, in others in both, has been known for a long 

 time. One of the first points to which the earlier experimenters 

 with Smerinthus hyhridus drew attention was this very fact, and 

 the same observation was made by Standfuss in the case of his 

 Drepana and Clostera hybrids, and by myself with the Biston — 

 Ithysia crosses. 



No satisfactory suggestions as to the cause of this displace- 

 ment have ever been made. That we have to look to the 

 disorganisation of metabolism due to hybrid origin is perfectly 

 clear, but how this is brought about is certainly not obvious. 



Cytological observations have shown that, in the case of 

 hybrids between species in which the number of homologous 

 chromosomes is small, gametogenesis occurs without reduction 

 division, so that in the gametes of the hybrid insects we have 

 nearly the somatic number of chromosomes present. This mode 

 of formation of gametes may be accomplished at a much greater 

 speed than in the case of a pure species, a feature that may be 

 accompanied by a correspondingly earlier somatic development ; 

 hence an earlier emergence of the insect than is usually the case 

 may be expected. 



A point, too, that possibly has some bearing on the case 

 is that, when some species are rapidly forced, a rapid appearance 

 of the imago is accompanied by immaturity of the sexual 

 products.* Possibly, then, the degenerate nature of the germ 

 cells, especially visible in some hybrid females, may react on 

 the somatoplasm and induce a precocious development of the 

 soma. The ova of the accelerated females of rohsoni are defec- 

 tive, as dissection and subsequent microscopic examination 

 prove. 



(To be concluded.) 



SOME NEW MELANIC EUPITHECIA ABEERATIONS. 



By Louis B. Prout, F.E.S. 



Mr. G. B. Oliver, of Wolverhampton, has sent for my 

 inspection some very interesting melanic Etipithecia, representing 

 in part species in which — so far as my knowledge goes — extreme 



* As in the case of Deilejyhila elpenor in my own experiments. 



