VARIATION AND HEREDITY IN TWINS 129 



2. Set K 13. Mother, 565; fetus I, 575; fetus II, 570; 

 fetus III, 563; fetus IV, 563. — ^Here we have one pair like the 

 mother; the other pair, presumably, like the father. 



3. Set C 29. Mother, 561; fetus I, 549; fetus II, 560; 

 fetus III, 547; fetus IV, S46.^-Here we have one like the mother 

 and three, presumably, like the father. In this connection it is 

 interesting to recall the relations of fetuses shown in Figs. 21 and 22, 

 where it appears that three fetuses may be derived from one half 

 of the ectodermic vesicle and one from the other; we would expect 

 the three from one side to be much alike and the one from the 

 other side to be somewhat different. 



Type IV. None of the fetuses are at all closely like the mother 

 and still show wide differences among themselves: Set C 65. 

 Mother, 543; fetus I, 561; fetu^ II, 563; fetus III, 573; fetus IV, 

 573. — ^The paternal number is probably at least as high as 573; 

 the others are partly paternal and partly maternal. Examination 

 shows that the first 5 bands are much like those of the mother in 

 fetuses I and II, while the last 4 bands are much like those of 

 fetuses III and IV, which are probably purely paternal. 



It is not rare to find good cases of types I and II 

 which show nearly pure maternal or paternal dominance 

 of all nine bands. Nearly 25 per cent of cases could be 

 classed in each group. The remaining cases fall in the 

 classes that show the various inter- and intra-individual 

 distributions of maternal and paternal dominance. One 

 comes to the conclusion that the armor characters are 

 examples of mosaic or particulate inheritance. The 

 maternal influence is largely dominant in some sets, 

 or in some individuals of a set, and the paternal in 

 others. There are also cases in which the influence of 

 one parent predominates in some bands, and that of the 

 other parent in other bands. Finally, there are some 

 cases in which one lateral half of the body has quite a 

 different number of scutes from the other half, and one 



