R C. PUNNKTT AND TIIK LATK l\ ii. HaILKV 



19 



of 4 months. For testing this |)oint the iivAilahli* n^conis consiHt of 

 ^^<f<f rtiul :iO ?? belonj(in^r to i\\v F., ^M-nonituui of tin- Flnuish- 

 mixtnl cross, together with U ^^f and 20 ^ ? of thf h\ g«n«THtion 

 from the Flemish- Polish cross. Both ^f ^f and J J in each wisr havr 



Ar«rM«irei«ht 



of mMH ttnn«r 



< lb*. Sot. 



TABLE ( 



A vermes wnlitht 



of malm of 



6 Ibi. S OS. and over 



AvcnMTc wriKht A veracv ««lcht 



of frttuuM under of frmiUM over 



7lbii. 



7 lb* 



At 4 At 13 

 month* month! 



t\ Kenenuiou from 

 Flemish -mixed 



35 



61 



Averace weicht 



of malet under 



4 Iba 8 OS. 



At 4 At 13 



months nionthn 



Fi generation from 

 Flem 

 cross 



^neration from ) 

 Flemish-Polish \ 115^ 41 



At 4 • At 12 

 moothn month* 



4-5 



7-2 



Avenu(o weight 



of malee of 



4 Iba. 8 OS. and oTcr 



At 4 



month* 



2-9 



At 12 

 month* 



4- 12 



At 4 At 13 



month* months 



313^ 0-2 



At 4 At 12 



month* tmmtlui 



313 



T-l.-ii 



Avvnwce weiKht Avera^rv weljcht 



of feniale* under of female* nf 



4 Dm. 10 ox 4 Ih*. 10 ox and over 



At 4 At 12 



month* month* 



2-4 



4«3 



At 4 At 12 



montliH month* 



2-2 4-14 



been divided into two roughly eijual groups, one containing the light<T 

 and the other the heavier animals. For each group the average weights 

 at 4 and 12 months respectively are shown in Table C. The result 

 shews that (^ff which are lighter at maturity are also markedly lighter 

 at 4 months, but that all the $ ?, heavier as well as lighter, are indis- 

 tinguishable in size at the earlier age. This result is strengthened by 

 the fact that it is equally true for the Flemish-mixed and the Flemish- 

 Polish animals. For the same chiss of material the bucks which are 

 destined to become heavier start to outstrip the lighter ones at an earlier 

 age than is the case for the does. 



Inbreeding. In so far as our limited experience goes close inbreeding 

 appears to lead to diminution in weight', and perhaps also to some delay 

 in the age of maturity. Decrease in weight is most marked in the axsc 



* This is contrary to the opinion of Huth ('87) who inbred rabbits for seven generations 

 to test this point. Though the average weight of his animals at the end of his experiment 

 was as heavy as at the beginning he does not state the numbers upon which ihese averages 

 were based. Nor does he give the weights of the parents in any case. His tigures do not 

 preclade the possibility that he selected the heaviest parents in each generation to breed 

 from, so that any efifect due to inbreeding might have been masked by unconscious selection 

 of genetic factors for increased size. That close inbreeding may be accompanied by an 

 increase in size, provided that the largest and most vigorous animals are selected for 

 breeding from, is brought out by the recently published experiments of Miss H. D. King 

 ('18) with rats. 



2—2 



