GENETICS IN SWEDISH FINLAD 



113 



of hybrids behave slightly differently in respect to the extent in which union in 

 pairs takes place. The cause of this peculiar behaviour of the chromosomes is 

 to be found in the fact, that the affinity between homologous chromosomes of 

 the same species is lacking between the chromosomes of different species, united 

 in the hybrids. 



Anachoreta 

 30Chr. 



Curtula 

 29Chr. 



Pigra 

 23 Chr. 



59 



Ag * Ctf 



58 59 



Pc> 



57 



59 Chr. 



ep 



P<J 



56 



Ag 



Cd) 



59 



- . 



'-Wtf ; ; 



|i*wV.j ".%.*. 



EXPLANATION OF PLATE. 



FIRST AND SECOND SPERMATOCYTE EQUATORIAL PLATES OF PYGAERA ANACHORETA, CURTULA AND PIGRA. 

 First spermatocyte equatorial plates of the hybrid anachoreta 9 x curtula c? with 5859 chromo* 

 somes, so that none or only two chromosomes have united to form a pair. All the others are 

 about half the size of the first and about the same size as the second spermatocyte chromosomes 



of the parent species. 



First spermatocyte equatorial plates of secondary hybrid P. anachoreta 9 x (P- anachoreta 9 x P- 

 curtula <J') c? with 56 and 59 chrosomomes, (latter in two sections). Of the chromosomes about 

 30 are large, and consist of two units, paired together, presumably anachoreta chromosomes; about 



26, resp. 29, are small, unpaired, presumably univalent curtula chromosomes. 



First spermatocyte equatorial plates of the reciprocal hybrids between P. curtula and P. pigra : the 



chromosome number is 4751, there is thus only 14 paired chromosomes, all others are univalent. 



The figures mark the chromosome number after the maturation*division. 



15 



