12 THE ENTOMOLOGIST. 



hybrids has certainly still less to do with the high percentage of 

 gynandromorphic forms. These were entirely pure females, 

 drawn direct from nature, which, according to experience, have 

 no inclination to produce gynandromorphic offspring. 



We are therefore limited, above all, to the condition of the 

 male parents, that is, as to the quality of their genital products 

 as the resulting factor. 



This with all the more surety, since the genital products 

 of the female hybrids of the same form had shown, even on 

 microscopic examination, various degrees of degeneration, or, 

 indeed, on microscopic examination, were found quite wanting. 

 The authenticity of this idea is supported by the fact that the 

 degree of fertility of these male hybrids is parallel with the 

 degree of development of the egg germs and eggs in the ovaries 

 of their sister females. The fertility of the hybrid male of the 

 crossing S. pavonia ^ x spini ? was constantly higher than that of 

 the male of the crossing S. pavonia ^ xp)in'i ? , just as the females 

 of the first hybrid have more highly developed egg germs and 

 eggs than those of the second. 



The condition of these male sexual products must, on their 

 side, undoubtedly be regarded as a result of the hybrid origin of 

 these forms, and depends to a large extent on the physiological 

 affinity of the species hybridized. The lesser the divergence 

 and difference of the crossed forms, the more normal will be the 

 qualities of the sexual products of the resulting intermediate 

 form. 



As the sexual products of female hybrids have suffered per- 

 ceptible damage and disturbance of their development through 

 their hybrid origin, so also have the sexual products of the males ; 

 the latter is perceptibly proved by the frequent failure in function 

 of these sexual products. Sometimes they do not act at all, 

 sometimes result in individuals of abnormal, that is, gynan- 

 dromorphic, build, and finally, sometimes at least, according to 

 their outward appearance, in thoroughly normally developed 

 males and females. 



From these results it must be granted that there are factors 

 which, passive in the normal male sexual products, cause the 

 development of the resulting individual in the direction of a 

 normal male or female build. 



Moreover, we saw from the figures that the germ of the 

 females of the two pure parent forms were by no means equally 

 influenced by the male sexual products of the same hybrids. 



The male hybrid S. pavonia S^ x ^>v?'? ? paired with imvonia $ 

 only produced brood in 33 per cent, of the pairings, which varied 

 in fertility from 4 to 62 per cent. ; the same male crossed with 

 pyri ? was infertile in more than 60 per cent, of all pairings, 

 and the fertile pairings only resulted in 1 per cent, offspring. 

 Hinderances of a purely mechanical nature are in this case 



