268 First ami Seeovd Toes in Man 



table A) of the A type. In one case both parents had L toe-type, but 

 the tracing of the father was unsatisfactory. Nothing is known of the 

 ancestry or sibs of the parents. The sister and brother of this case were 

 undoubtedly L. The second case of a female A is seen in Fig. 5, 

 Tree D, where an S gi-andparent is known, and where, therefoi-e, the L 

 father may be a heterozygote. 



Unfortunately I only obtained two uiatings of S ^ y. S % ; these 

 produced nine offsjjring, eight 8 and one L. These numbers are far too 

 small, but they seem to indicate a tendency to breed true. One of the 

 families is seen in Fig. 5, Tree E, (iii). This tree shows side by side two 

 family gi-oups (ii and iii) wliich certainly suggest segi-egation, and here 

 the offspi-ing are numerous enough to make the results impressive. 



The next mating analysed is 8 % x L ^ and L % x 8 ^. These 

 25 matings gave 80 offspring, divided thus, 58 L,\0 S,\l A and B, 1 E, 

 or 58 L and 22 of the other types ; here there is partial dominance of 

 the L over the iS type, approximately 2| to 1, suggesting either that 

 there are several factors which make up the final result, or that some L 

 type parents wei'o not pure. If 8 is the ix'cessive type, as appears from 

 this crossing and others yet to be studied, how can any 8 arise as the 

 result of the X ^— ^ *S' ci-oss ? The i'Xj)lanation is to be found in the 

 probability that a few L types are lieterozygous : this would also 

 account for the few A and B typt's found among the descents of L y. L. 

 Of the 25 cross-matings, !) only have any iS' offspring, and of these enough 

 is only known in one case to suggest an explanation. This history is 

 seen in Fig. 5, Tree F. The grandmother here is an 8, so that the 

 father may be a heterozygote. 



There were 31 matings of Z x ^4 and L x B, producing 124 offspring, 

 85 Z, 12 ;S', 11 A and B, or 85 L to 28 of the other types, approximately 

 8|- to 1 ; again the L type shows its dominance, and as would be expected 

 if A and B are the hetei'ozygous forms, thei'e is a larger projjoi'tion of // 

 produced than in the L x 8 matings where the L offspring are to the 

 " other" type offspring as 2| is to 1. 



The appearance of any 8 type is not to be accounted for in this 

 cross, unless again, some L are heterozygous. Amongst the 31 matings 

 9 only produced the 12 >S' offspring. In 7 of these matings nothing 

 is known of the ancestry of the L parent ; in the eighth case the L 

 parent is one of a jjure L fraternity and there is therefore no collateral 

 history. In the remaining case, the L parent had a pure L ancestry 

 but had a sister who was A type. It should be noted that of the 12 8 

 offspring, a large proportion, 10, are females. 



