GENETICS IN SWEDISH FINLAD 115 



a living chrysalis, which afterwards gave a typical hybrid imago male. As por= 

 cellus and elpenor by certain authors are considered as belonging to different 

 genera and must certainly be regarded as good linnean species, one would have 

 expected a reduced affinity between their chromosomes. 



Later on quite analogous phenomena like the ones described by me in the 

 lepidopterous hybrids, are pointed out in the maturation of the gametes in spe* 

 cies hybrids of mammals, birds, other lepidoptera, and a great many phanerogamae. 

 Thus it appears, as if the conclusion were warranted, that the lacking power of the 

 chromosomes to mate was a characteristic of most species hybrids, and further, 

 as if a tripleentente of chromosome affinity, fertility and segregation stood against 

 a triplealliance of chromosome repulsion, sterility and constant=intermediate inherit^ 

 ance. It would be of greater interest still to try and get this hypothesis confirmed 

 through continued attempts at crossings between different species and races. 



But even otherwise the experience thus gained is of general interest. It 

 shows, that at the side of the alternative or mendelian type of heredity, another 

 type exists, that is, the constant^intermediate one, which is however of lesser 

 significance, as it must always in its most extreme form produce sterility. But 

 both these forms can also exist side by side in the same hybrid individual, as 

 has been proved at least in one case. I refer to the fact that some chromosomes 

 unite, while others do not: then all the factors, situated in the paired chromo* 

 somes, segregate, all those in the not united chromosomes, show a constant* 

 intermediate type of heredity. In reference to the latter factors, not pure gametes 

 are formed. But these are not a result of an amalgamation between inherited 

 factors, as was generally assumed earlier, but on the contrary produced by the 

 slight affinity between the strange chromosomes, through which the mechanism, 

 needful for mendelian heredity, is rendered incapable of functionating. 



An earlier opinion was, that mutations and new combinations were the only 

 ones to be reckoned with, when new species arose. However, I am of opinion, 

 that the new forms arising out of new chromosome combinations, could be ima« 

 gined to play a not quite unimportant part, and especially with regard to lepidoptera 

 might explain the very much varying chromosome number we find in this order. 



From a cytological point of view, too, the observations thus made are of no 

 slight interest, for they show, that chromosomes retain their individuality, though 

 they have existed for two generations in a foreign cytoplasm. Continued examina* 

 tions, especially with regard to the heterochromosome behaviour, of great value in 

 moths, will doubtlessly afford new and interesting ideas. I am going to cite one here. 



The hybrid between P. anachoreta 9 and curtula cf is interesting, in so far 

 as the larvae show a sexual dimorphism of highest degree, a fact which is very 

 rare among the lepidoptera and of which the parents do not show the least trace. 

 The female hybrid larva is always like the father species curtula, but becomes 

 much larger than the aforesaid and grows very slowly. The male larva, on the 

 contrary, is on a whole like the mother species anachoreta, of the same size and 

 developes as quickly. The larvae in the reciprocal cross are however exactly alike 

 in both sexes and impossible to distinguish from the said male hybrid larvae. 

 Thus it is to be assumed that this is a case of criss<cross inheritance in a species 

 hybrid — to my kowledge the first known one. The back^crossings made with 



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