2O H. H. NEWMAN. 



Fetus III. has the doubling of band i, beginning 4 scutes from 

 the left. The symmetry is the same as that of the mother, but 

 a reversal of that of the opposite individual, fetus I. Fetus III. 

 is therefore a mirror-image of fetus I. 



Fetus IV. has the anomaly beginning after 3 single scutes from 

 the right margin of band I. The symmetry is a reversal of that 

 seen in its twin partner, fetus III., and of that of the mother, so 

 that III. and IV. are mirror-images of each other. 



This set shows clearly that a double scute is genetically equiva- 

 lent to a double band. It is seldom that one finds a set showing 

 such extensive reversals of symmetry. 



Set C. 29, rf 1 (Table Bi}. 



This set is the complement of set C. i, in that the mother has 

 an extensive band doubling and the offspring inherit it in the 

 form of scute doubling. 



The mother has in band I beginning 4 scutes from the left 

 a doubling extending to the right margin. 



Fetus II. has in band 7 the second scute from the right double. 



Fetus III. has in band i and in band 8 just to the left of the 

 middle a double scute, and in addition a double scute 8 scutes 

 from the left in band 8. 



Fetus IV. has in band 3 a double scute in the ninth position 

 from the left. 



This set illustrates an extreme case of positional shifting of a 

 genetic character. There can be no question of the relationship 

 between the two scutes of fetus III., occurring in band i and 

 band 8 just to the left of the middle. This is a case of reduplica- 

 tion of inheritance unit along the antero-posterior axis. Similarly 

 scute 8 in band 8 of fetus III. and scute 9 in band 3 of fetus IV., 

 are expressions at different levels of the antero-posterian axis 

 of the same genetic unit. 



The double element next to the right-hand margin of band 7 

 in fetus II. is certainly the same genetic unit as the element next 

 to the middle of band 8 of fetus III., but with a reversal of 

 symmetry. Thus by the application of the principle of sym- 

 metry reversals and reduplications down the primary axis we can 

 connect up even such apparently unrelated units as these. 



