LIMITS OF HEREDITARY CONTROL 901 
expression. Evidently a marginal fusion of bands 1 and 2 is 
predetermined, but here the predetermining influence ceases to 
operate and epigenetic factors of some sort determine whether 
the character shall have a unilateral or a bilateral expression and 
to what extent the fusion is to be carried in each case. It will 
be noted that hereditary control is much less precise in this case 
than in set 64. 
2. The ‘three-to-one’ proportion once more presents itself in 
that three members of the set have the fusion on the right side 
only, while one has it on both sides. 
Fig. 4 Diagrams of the ‘abnormal’ bands of the four foetuses from female 
no. 96. 
3. There is a distinct pairing on the basis of the extent of the 
fusion, pair A (1 and 1) showing the character in a much less 
extensive form than pair B (ar and Iv). Within the pairs the 
resemblance is very close. 
Set 101 (Mother normal). The conditions seen here are in 
many respects equivalent to those described for set 64. All 
four foetuses show a rather advanced stage of splitting in the first 
band. At first we thought that foetuses 11 and Iv were quite 
