59'i i\' (,(iM-i;iii:\(:i-; intmiwtkiwi.k nr. (.knkiioi K. 



observée! in Mcndelian liybrids is duc rallier lo tlie niitiuc uT llic cliromosomes 

 l'romthe dillereiil parenis tlian lo llieir rolati\(' posilioii iu llir s\ii«,ramic nuclei. 



Tlie tliird condition, proliably noi'mal in wiid specics, is thaï in wliicii Ihe 

 chromosomes l'reely inlermingle at tlie moment off'ecundalion, Ihc confiffuration 

 thev then lake on accidentally being perpeluated throuf^lionl llie Hle ot" Ihe 

 individual. I he dilïerent chromosomes exerl varviniJ' dej^rees of influence on 

 the cell, de])ending on whelhcr liicy aie localed iicar Ihe peiiphciy nr near Ihe 

 cenler of the niicleus'. 



The foUowing synopsis exhibils Ihe Ihree types of feciindalion. 



I. Intluspecific iiYBRins : Usually stérile and inlermediale. 



^'iolenl crossbreeding. Chromatie material tends lo remain separale; 

 synapsis often impossiJjlc, resulting in sterility. 



II. Mendelian crosses : Usually intermediate, dialytic al synapsis. 

 Mendelism, crossing of inbred hybrids \\ith imperfecl or false synapsis. 



III. NoRM.vL CROSS-BHED sPEciEs : Usually vigoi'ous, ferlile and variable. 

 Normal crossbreeding. Chromosomes l'reely inlermingle al moment ni 



lecundalion and the configuration lliere laken persisls through the ontogeny 

 of Ihe individual, giving greal variely of forms. Synapsis noiinal. 



As lo the fact of considérable variations in firsl génération liyluids of rela- 

 tively stable species or races there can be no doubt. 



In the light of what lias been said al)Ove, il cannotlie doubted thaï vve hâve 

 in such variations a vital and important priiiciple of heredily and one which 

 goes far lo e.\[)lain many obscure plienoniena of Ihe everyday expériences of 

 animal and plant breeders. 



The suggestion, lirst madc in IS'J7 and hère r(>ilerated, thaï such variation 

 may, in parlai leasl, be due lo positional différences in the material bearers of 

 hereditary characters is of course merely a provisional hy|)othesis As such il 

 may prove helpfui in gclting a clear idea of the phenomena lo ])e explained 

 even ii il does not aiil us materially in such an explanation. 



Cook* has pointed oui thaï Ihis theory, of positional relations of the idio- 

 plasmic materinls of Ihe cell. puis a nc\v i-esoiirce in the Iiands of llic evoln- 

 lionisl in llic sliidy of Ihe baftlingly coiiiplcx expression rclalions of licreditar\ 

 characters. 



Il is casy lo sec Ihat ifwcaccepi Ihe li\ polliesis of lli(> |iosilioniil rclalioii 

 of chromosomes, a very large number ofdilferenl forms could be expecled lo 

 occur among hybrids of the same relatively pure-bred parents. In Ihis way Ihe 

 praclice of almost ail successful plant breeders in selecling tiie jjest individuals 

 from among a large number of hybrids receives a nevv justification. 



In order lo bave a name for Ihis supposed positional innuence of Ihe 

 parental idi()|ilasm in tlie cells of cross-bred individuals, 1 |iro|)ose Ihe term 



lîy zygolaxis"' we nienii the arrangenienl in liu' >\iigaiuete (zygote) of the 



1. Tlie law iil' lilial i-egi-cssiciii iliscovoroil by l'i-amis Gallon Saliiml liilieiiliiiin-. M^.iMiil.in i:,i.. 

 188!). pp. 9."), et seq.) may in part be explainablo as roproscnliiij; tlie iiicasiiic ol' Ihe cxlrni \„ «hidi 

 tliese accidentai roiiligiiralions ai'O wipod nul (Inrinn llic siiciccdinp synapsis. Il' sni-li i-iiiiliL;uialiiins 

 were complelely wiped (inl, lilial rPL;i-essi(in Udidd lu' noinialh KKI 11 in-hMil ..I M.inriliin- liKr 

 r.5 0/0as foniid by Gallon. 



'2. Cooli, 0. F.. l'.HO. .Mnlalive levcisidns in cnlkin. Ciicnlar n ,').'.. I;.IM,,I .S. nr|,l. A-iii.. p. \7, 

 Mai-. 21). 



7>. l'Yom r-j"rV(. Vdko (l'or zvmlc , and -dh:. arran"i'nii'nl. willi leli'riaicf lo llir i.ii-l lli.il sm-li an 



