LIMITS OF HEREDITARY CONTROL 889 
Set 121 (Mother without any double scutes) 
Foetus 1. No double scutes 
Foetus 1. In band 2, scute 29, double 
Foetus 111. In band 2, scute 28, double 
Foetus tv. In band 3, scute 28, double 
It is to be noted that in three of the four individuals the double 
element occurs practically in the same spot. In view of the fact 
that, even in perfectly normal sets, the number of scutes in the 
same row varies widely among the individuals, it would hardly 
be expected that a predetermined doubling could strike the same 
numbered scute in any two members of a set. The regional 
hereditary control in this case is therefore somewhat more accu- 
rate than we would expect to find it, in viewof the laxity of hered- 
itary control in the matter of the arrangement of scutes into 
bands. The fact that in one of the foetuses the double scute 
occurs on the third band, while in two other foetuses the 
doubling affects the same or contiguous scute of the second band, 
only goes to bear out the idea that the process of scute alignment 
is to a large extent a mechanical process, involving the shifting 
backward or forward of the individual primordia under the influ- 
ence of pressures. It is only to be expected then, in the light of 
these considerations, that we should find a case now and then 
where a readily recognizable element like a double scute should 
indicate by its position that it may have been shifted from one 
row to another. 
On account of the small extent of its ‘abnormalities’ this set 
has been used in the study of correlation (table 6, A) as well as 
for an example of a peculiar type of band arrangement, (p. 874). 
Set 128 (Mother without atypical scutes of any kind) 
Foetus 1. In the last row of the scapular shield, scute 30 is double; scute 2 of 
band 2, double; scute 10 of band 3, double 
Foetus 11. In the last scapular row scute 28, double; an incomplete scute like 
that shown in fig. 9, occurs in band 6 between scutes 2 and 3 
Foetus. Inthe last scapular band scute 14, double; scute 49 of band 6, double 
Foetusitv. Scute 31 of band 4, double 
