THE SKX RATIO IN HYBRID RAT-. Ill 



liyp<>the>i- that tin- male i- tin- -e\-deierminin- factor seem? t<> 

 necessitate tin.- further a umption that fertili/atinn is selectixe 

 when individuals belonging to different race- are cn---ed, the 

 egg offering greater n-i-tancr to the entrance <>t a -permatn/oan 

 ilia; i- female-producing than in <me tliat i- male-producing. 

 Then- i- link- r\ idi t, that fertilization is ever selective. 



Tin- pn.li.diility of it- <>< rurrciice as a normal phcm >meii m ha> 

 ently been advocated bj \\< .i\ although Wil-m '10 



considers ii "SO iinpr-'haMc as alum-l 1" inxalidalr an> inti-r- 

 l|-ciaiin into which it i-nti-: 



Guy< lia- -h(i\\n that thnv i- t .n-idi-ralilr amount nf 



dr^i-iu-iMiidii in tin- t. : many luhrid i>ii;i-('n-: almonnal 



mitoses .md mi>-hap-n -jn-nnal< /( >a lx iiu "t trniiu-nt occnrrciicr. 



( )tln-r nli-rr\ IT- li.r. d thai the gonads in hybrids are 



o|- It--- drfci ii\i-- lull in-ill- "1 them ha\c made a lii-li -l 

 in\r-iiv;alion in "idi r i-> a- rlain \\hat -liiKMir.il i hani^cv ha\i 

 n pr..dinrd. Guyer's '!-- i \ alii-n- .-tn.inj\ -nc^r-l that 

 ill- -| \.ilm- ma\ In .-lit.iiiu-d h\ a -lu<l\ <-t the ^miad- in 

 otlitT li\ lirid-. M. iii-rial i- ln-in^ collected for .m inxf-ti^ation 

 of tin- cmiad- in h\l>rid rat-, in the hope that it \\ill at lea-l i;i\c 

 --me (hie i- the i.ui-e fi -r the iiu iilit\ in -nci ei diir^ 



^eiieratii-n- <>! li\liri-l-. e\eii it ii .ill"nl- n- e\ ideiice that \\ill 

 en.il-le i.ne [ off( \planati-n f- -r the altered 



ratin in h\ hrid fi -rm-. 



I I II-K \ 1 l Kl- i I I I 

 Bos. Rit/cma. 

 '.J4 LJntei ' : ^.ui.!-. I 



\1\ 



Crampe, Dr. 

 '84 /in in '. .iiiiiifii \v ii R.W iltati dei K- 



/. ili in. i, K.iiti-ii mil \\il.l. n. l.in.luin! fahrl . IM.XIII. 



Cu^not, L. 



'99 Sur la .li-triiiiiii.iti-'n <lu * . I'-ui': 



ilc l.i M-i^ii|i:.-. I 

 Davenport. C. B. 



'06 Inliniuiiii in l'"iilti\. I'.il' ' .;-'. 



Dusing, K. 



'84 I>i- K-xiilH-iuiii; -\.-iluilf.. i -li-ii \'C-IIII--|IIIIIIK 



Menachen, riere, un.l I'll.m/'-n. Ji-n. /'-it-iin. Naturwiss., H-l. X\ll. 

 von Fischer, J. 



'74 Hi-nli.i. lit iir.^'-n uebei Ki' : "ini;i-ii \-rr-iliii--lt-iii-r l-'.ti l ii-pii-Lu t< 11 innci- 

 Imlli ei] -'I t''ii. H'l- X\ 



