l6o DR. K. W. DAMMERMAN, ON HYBRIDS KTC 



chitination. In all respects it is very similar to many of its 

 allies. Albofasciata is the same in ail details, the sac is the 

 same length and the "armature" cannot be recognized from 

 that OÎ gigas. The hybrids are the same, as was to be expected". 



From the obtained results one may deduce that the deviating 

 • forms which 1 had caught some time ago, as well as those 

 reared by me, are actually hybrids of albofasciata ?i\\âi gigas. 

 With the free-living species such h}'brids are rareh' found, 

 norwithstanding the fact, that both species regularly occur 

 side by side in great numbers. As long as the animals are 

 free to select, they onl}' mate with their own species, pairings 

 between the two species will be very accidental. 



The above described hybrids remind us strongi}" of another 

 species, viz. Batocera t/io)>isoni]\\. ; this species much resembles 

 the gigas but as a rule shows one row of white spots (the 

 second row) while one or two other rows ma}' occur besides. 



It is however not probable that the tJiomsoni is a h)'brid of 

 gigas and albofasciata^ as thojnsoni occurs in the isles of Sumatra 

 and Borneo, while the gigas is only found in the isle of Java. 



Not much ma\' be added to the afore-said cross-breedings ; 

 we can onh' guess at a possible explanation. 



In connection with that, which Federlkv found with Pjgaera- 

 hybrids ^), one ma}' conceive, that the egg-cell principally 

 develops parthenogeneticalh' and the paternal nucleus can 

 only parti}' influence it and is rejected for the greater part. 



Not onl}' would this explain the matrocline character of the 

 h}'brids, but also the difference in sex-ratio with the pure 

 races and the h}brids. One often sees in parthenogenesis with 

 insects, that the öftspring is for the greater part of one sex. 



Cytological investigation might throw some light upon 

 this, but the sterility of the h}'brids and the fact that these 

 are very difficult to rear in greater numbers remain an 

 obstacle to the further stud}". 



Bussum, Febr. 1919. 



>) P^EDERLEV, Das Verhalten der Chromosomen bei der Spermatogenese 

 der .Schmetterlinge Pygaera aiiachoreta^ curtiila und pigra, sowie einiger 

 ihrer Bastarde. Zeilschr. für Ind. Abst. u. Vererbungslehre Bd. 9. 191 3. 



