THE LIMITS OF HEREDITY i8i 



may have its greatest expression early in ontogeny, 

 before birth, and that it may be induced either by 

 hereditary or other factors. The twins showed 

 marked similarit}^ in their friction ridge patterns, 

 also in the muscular and arterial systems of their 

 hands, some similarity in nerve distribution, but 

 practically no resemblance as regards the veins. 

 Compared with the control hand, these resemblances 

 indicate that heredity is the chief factor involved in 

 the variations observed. 



Newman and Patterson (191 1) have made a study 

 of the inheritance of peculiarities in the scutes or scales 

 on the nine bands of the armadillo, and similar 

 phenomena to those above mentioned (p. 179) appear 

 in their quadruplets, but in all these cases the father 

 is unknown. Thus, in one set of quadruplets three 

 show a double or abnormal scute, and one lacks it ; 

 in another set three have the scapular double scute, 

 and one lacks it. Other sets of quadruplets show 

 more variation in the position of. abnormal scutes, 

 but the evidence indicates that the latter are, at any 

 rate, blastogenic or predetermined in the egg. The 

 authors attribute these divergencies to inaccuracy 

 in the bilateral distribution of hereditary materials 

 during development — in other words, to somatic 

 segregation. The element of heredity cannot be 

 accurately judged without a knowledge of the male 

 parents. The process of scute alignment is shown to 

 be largely mechanically determined, and hence beyond 

 the limits of hereditary control. 



Newman (191 6) finds in armadillo quadruplets a 

 condition of symmetry between that observed in 

 double monsters (whose whole development has been 

 in contact), and human duplicate twins. Hence he 

 concludes that the latter become ''physiologically 

 isolated " (this may imply asymmetrical nuclear 

 divisions of cells whose descendants remain tor some 



