LIMITS OF HEREDITARY CONTROL 899 
Foetus 1 shows a condition entirely different from that de- 
seribed for its partner, namely a bilaterally symmetrical, regional 
splitting of the first band, beginning four scutes from the margin 
on each side and involving 15 double rows of scutes in each case. 
The condition is diagrammatically shown in fig. 3, 1. 
Foetus 11 exhibits a decidedly asymmetrical regional splitting 
of the first band, being a mixture of the two pure types shown in 
foetusestand iz The left half of the band is identical with that 
of foetus 11, while the right half is the duplicate of that in foetus 
1 (hie 3, Er): 
Foetus Iv is identical with foetus 111, in so far as the splitting 
is concerned, but shows in addition to the latter a fusion of the 
anterior row of the completely split half with the opposite half 
of the last scapular row of scutes. This condition has been ob- 
served in the shells of several adults and has been interpreted as 
a case of the incipient addition of a band to the banded region by 
means of a ‘drop-down’ from the scapular shield. The present 
condition could hardly be interpreted in that way in view of our 
knowledge of the conditions seen in the other members of the set. 
It would appear that we have here a case of an epigenetic process, 
involving a secondary fusion of two unrelated half bands, the 
right half of the first band and the left half of the last seapular 
row (fig. 3, Iv). 
This is in some ways the most extraordinary set in the collection 
and suggests a number of theoretical considerations for general 
discussion. The main points that should be noted while the facts 
are fresh in mind are as follows: 
1. The splitting process involving the first band occurs in all 
members of the set, which would indicate that this much was 
predetermined. 
2. The regional splitting involves in all four cases (twice in 
foetus 11) exactly the same number of scutes, 15 in each ease; 
and these are located precisely the same distance from the margin 
every time. The precision of hereditary control is, in this regard, 
nothing short of marvelous, since it is perfect. 
3. There are evidently two distinct expressions of the splitting 
tendency, the complete and the incomplete. The distribution of 
