W. s. WIMil.K. — WIIIATKIN IN KlliST (,KM;i; AÏION lhl;l!ll)S. ."Ol 



brids of tlio first g-pnei-olion is iluc lo a more complote inlormingling ot' llie 

 heredilary parliclos in case of polymoi-phic hyljrids (olls[)rint>- of closely relaled 

 organisms), whercby many ditTering combinations would be possible, and in 

 case of uniforra hyln'ids (moslly oll'spring of dislincl species or very dilTerenl 

 races of tbc same species), to grcaler or less aversion lo commingling belwoiMi 

 the Iwo more diverse sorls of parlicles, wiiereby Ihey would icinain in Iwo 

 separale groups and afi'eci, onlogeny uniformly and ciinally'. 



Since Ihis announcenienl was nuule some évidence lias jjeen pidilishcd' lo 

 show not only Ihal individual chromosomes persisl Ihrougli llie so-calli'd rcsling 

 stages of Ihe nuclens but aiso liiat Ihe particular conliguralioii is preservcd 

 from one cell génération to anothei' svitii some accnracy. 



It seems not improbable Ihat this theory of a |iiisili(inal or M'cloiial 

 inflni-nce of chromosomes may be further ami'nd<'d liy assumiiig thaï Ihe 

 chromosomes which happcn to lie nearest Ihe niicicar wall and, ex /lypol/icsis, 

 thereby exert the grealesl inlliience on Ihe cliaraclcr of Ihe cells conlaining 

 them, are liUcvvise betler nourishcd Ihan the chromosomes localed near the 

 center of the nuclens which are Ihereby prevented both from exerting Iheir 

 full measure of iiiflnencc on Ihe ileveloping cell ami l'nini receiving Ihe mosl 

 abundant nourishnient. Il might be su]iposed that llic wcll nourishcd chi'omo- 

 somes which from their superficial position on the nuclens had been prépondé- 

 rant in delermining Ihe cliaraclcr of Ihe individual would also dominale during 

 synapsis and l<'nd lo givc as a r-csnll gamètes similar in llieii- hrreditary 

 character lu Ihe lirst gciieralidu liybruls whose characlrr was dclcrniined liy 

 the configuraliou ol' Ihe chromosomes which accidcnlally eauie aboul al Ihe 

 moment of fusion lielwcen Ihe nuclei of Ihe syngamete. 



Three lypes of nucleai- contiguralion migliL be assnmed to occur in Irgher 

 organisms. If a \iolcnt cross be made, very unlike species being hybridized, 

 the paternal and maternai chromosomes might repel each olher and occupy 

 opposite sides of the syngamete nucleus, exerting equal influence upon Ihe 

 dcveloping organismand asa consecpuMiee Ihe lirsl génération hybrids betwcen 

 widely distinct s|)ecies are ofteii but \t'ry slighlly variable and are alniosl 

 strictly intermediale betwcen the two parents. Such hybrids are usually stérile, 

 that is to say, the chromosomes are so unlike that synapsis (milapsis) cannol 

 occur The mule is a siriking exaniple of this class ol' liyltrids, which are also 

 common among plants. 



The olher exlreme is seen wiien abnormally inbred races of domesticaled 

 animais and plants are crossed. Such forms are likewise usually intermediale 

 in the first génération and are fertile. Ihe nuclei being able to pass Ihrough 

 synapsis and form fertile gamètes. TIk' synapsis, however, is more or le^s 

 inperfect and the paternal and maternai idioplasmic particles may not, properly 

 speaking, fuse or blend at ail but go over more or less unmixed to the resulling 

 gamètes. Possibly bccause of long conlinued iiai'row breeding and resulling 

 great affinily for a non related mate, the pairs of chromosomes might remain 

 juxiaposed in Ihe lirst génération, preventing much veclorial influence during 

 the first génération. The dominance of certain characlers which is regularly 



llronrs (.r llrrnliH ;ill(l „[ llu- ori.uill oi S|HM'ios cnllsidriva in ivl.-|- 

 loli |.\b■^l|•l.il, IN ll,hii,iail r.airllr. 'i,'. : I I I -1 IT. ' ii. 1! Irh.,. 

 !■, l'Kli.. r.nifhiii^sr „l,n' itir hniisl it 'il mu dn- rlirniiuillxrlr'i, Suh- 

 -W .Irll;, KlM-|i,.|M. 



