178 THE MENDEL JOURNAL 



In Pedigree C we have the results of a study of the 

 inter-relationships of four twin-bearing stocks, among 

 which twin births may be seen to have occurred at least 

 ten times. 



A reference to the chart will show how a man (B. 5), 

 whose sister (B. 7) was grandmother of homosexual male 

 twins (D. 66 and 67), marries a woman (B. 15) two of 

 whose nieces (C. 20, 22) had each given birth to twins 

 (D. 75, 76 ; and 77, 78). Of this union there was an only 

 child, a daughter (C. 8), who in her turn married into a 

 didymogenous stock, her husband (C. 7) having a brother 

 (C. 2) in whose family there were twins (D. 17 and 18), 

 and two sisters (C. 4 and 6) who were each parents of twin 

 children (D. 25, 26 ; and 31, 32). This second pair had 

 ten children (D. 41-50), and their youngest child — by some 

 curious instinct or fatality — again married into a twin- 

 bearing stock, her husband's uncle (C. 10) being a father of 

 twins (D. 63, 64). One can hardl}^ be surprised at learning 

 that on the normal termination of her second pregnancy, 

 in July of 1910, she was delivered of twin children (E. 6, 7). 



It is not necessary in this case to go over the individual 

 members of these families with the same detail as has been 

 given to pedigrees A and B of this series, for a glance at 

 the accompanying chart is really all that is required to 

 place one in possession of the main facts of the case. The 

 symbols, letters, and numbers have the same significance 

 as in the other pedigrees. 



It will be seen, however, that in many instances the 

 sex-symbols are not filled in for this case. But where in 

 the compiling of a pedigree of this sort too minute and 

 particular enquiry is made as to non-essentials, it is at a 

 risk of wearying or irritating the various persons who have 

 to be interviewed and questioned with a view to arriving 

 at the facts, a result which in my own experience has more 



