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it enables us to interpret the vertebral columns in the second, smaller 
group. 
One need only suppose, that the divergency of the direction of 
development increases more or less, then forms must originate that 
do no longer fit in the frame of the separate stages, but are con- 
nected with every stage as accessory forms, as they might be called. 
These forms remain by local, relative retardation or by local 
acceleration of the transformation, either below the stage, to which 
they belong, or they are a little more developed. But always they 
diverge from the direction that leads from one special stage to the 
other, and thereby they form, as it were, side-branches, which are 
however very short, because the several accessory forms are, as a 
rule, only represented by one single specimen. 
The second group contains 20 vertebral columns, and these represent 
17 different forms that can be denoted by formulas. 
Only as one single example I wish to cite an accessory form, 
belonging to stage //. In this stage the 20% vertebra is the 13th 
dorsal vertebra; if this vertebra through comparatively too rapid 
transformation becomes a first lumbal vertebra, whilst the other parts 
of the vertebral column remain unaltered, then a vertebral column 
has been formed with 6 lumbal vertebrae. And we see that this 
column has not followed the line of development leading to stage //a, 
because to this stage only 4 lumbal vertebrae belong. It has followed 
a side-path that leads away from the main-route and soon ends. 
Let me mention a second example. 
In the list of formulas stage ///b is followed by a hypothetical 
stage ///c, in which the 19 vertebra is a dorsolumbal vertebra. 
] have now found a vertebral column, belonging to the second group, 
in which the 19'" vertebra has this form. To the left exists a pro- 
cessus lateralis and to the right a rudimentary 12" rib, which is 
about to fuse with the vertebra. 
Further we find 4 lumbal vertebrae and a sacrum, consisting of 
6 vertebrae, the 24 to the 29, as must be the case in a stage ///c. 
In so far everything agrees with what is indicated in the hypothe- 
tical formula. But the vertebral column I am dealing with, bas only 
3 caudal vertebrae and not 4, as the formula requires, the 32"4 
vertebra is the last. 
Consequently I cannot regard this vertebral column as a repre- 
sentative of a stage ///c; but it may be conceived as an accessory 
form to such a stage. By acceleration of the transformation at the 
distal end the 33rd vertebra has been reduced comparatively too early. 
It seems to me that this observation makes it very probable that 
