OCCURRENCE OF TWINS 175 



Nos. 11 and 12 were twins. There were two after- 

 births. Both had fits in infancy. Both living in 1911, 

 and then nine years of age. 



No. 13. Suffered from laryngismus stridulus. 



Explanation of Pedigree A. 

 Occurrence of Twins in Successive Generations. 



The symbols and numbers have the same significance 

 as in the Pedigree for Lenticular Cataract (p. 172). The 

 solid black symbols indicate twins, where the sex is 

 known. Where tradition was defective, as in Nos. 18, 

 19, 20, and 21, C Generation, the thickened fraternal 

 (vertical) lines have the same meaning. 



Symbols with cross hatching indicate persons who 

 have had nephritis or vesical calculi or both. 



d.y. = died young. 



i.f . = suffered from fits in infancy. 



i.f.d. = died from fits in infancy. 



I.U. = incontinence of urine. 



L.S. = suffered from laryngismus stridulus. 



Ne. = died of nephritis. 



R.D. = suffered from Raynaud's disease, 



st. = stillborn. 



T. = twins. 



V.C. = suffered from vesical calculi. 



V.V. ^ suffered from varicose veins. 



Pedigree B. 

 Occurrence of Twins in Successive Generations. 



In this clanship of thirteen families, twins have 

 occurred in no less than six, eight sets of twins having 

 been born to these six families. In five of the families 

 twins occurred only once, but in the other family of the 

 twin-bearing group twins were born thrice. 



Unlike the case shown in Pedigree A, there is in 

 this one no uniform tendency to the production of 

 twins only towards the end of the family. In one case 

 only of the six is this shown, i.e., in Nos. 64 and 65, 

 Generation D. In the other families they occur indiff- 

 erently. Nos. 18 and 19, 27 and 28, Generation D occur 

 near the beginning of the family in each case, appearing 



