82 ROSS G. HARRISON 
On this account the operations in each class have been reduced 
to a common basis. While the probable error of these figures is 
in most cases large, the comparisons resulting therefrom are 
no doubt much more reliable than those resulting from the 
figures of the actual experiments. They are given in the last 
column of table 5. 
In examining this table we find that there is little or no asso- 
ciation between the experimental results and the following quali- 
ties of operation: homopleural vs. heteropleural, dorsodorsal vs. 
dorsoventral, vertical vs. horizontal, anterior and dorsal vs. 
posterior and ventral, the deviation from total lack of associa- 
tion (50 per cent) being in the most extreme case but 6.1 per cent. 
When we examine the figures with reference to the pair, homo- 
geneity vs. heterogeneity, we find that there is a much wider dif- 
ference (27.7 per cent as compared with 72.5). This would have 
to be regarded as a significant difference but, as will be seen below 
it is only secondarily so. The marked association between the 
harmonic combinations and normal development (93.9 per cent) 
and the very small proportion of normal development (6.25 per 
cent) in the disharmonic group, show that it is largely this pair 
of attributes that determines whether development will be normal 
or not. This quality of harmony or disharmony, however, is 
not like the simple qualities of side of origin, orientation, or direc- 
tion of the incision, but is itself a combination of two of them. 
Those that are harmonic are the homopleural dorsodorsal and 
the heteropleural dorsoventral combinations, the other two being 
disharmonic, as in the experiments with whole limb buds. 
When we consider the homogeneous and heterogeneous com- 
binations, we find them unevenly distributed with respect to 
the harmonic and disharmonic. This is on account of the restric- 
tion of operation due to the semicircular shape of the trans- 
planted pieces, which makes half of the combinations impossible 
of execution. Were these all possible, there would be complete 
symmetry in the aggregation as a whole. In reality, it will be 
recalled, six of the homogeneous combinations are disharmonic, 
while only two are harmonic. On the hypothesis that it is the 
harmony of the combination that determines normal develop- 
