58 
~ 
logische Reihe) that when describing the forms I could hardly help 
assigning a share in this description to the part of the phylogenetical 
development that is to be inferred from this chain. 
Because the separate forms can be joined together freely and in 
a definite direction to a morphological succession, it is clear, that 
there is no contrast between a normal form of the vertebral column 
and varieties. All these ten forms are principally of equal value; 
they are representatives of stages of development, following each 
other successively. 
The so-called normal vertebral column is the form that is at 
present numerically predominant. : 
Vertebral columns representing the formulas /f to /// are retarded 
forms that have stopped at different stages, preceding stage ///. 
And of course forms with a formula as ///a or ///b must be 
regarded as forms of a higher development than the normal vertebral 
column, having the value of future forms. 
It seems to me that this view is more satisfying than the other 
and at the same time admits of the possibility of a certain appli- 
cation, which the other does not allow. 
The application, I mean, becomes evident, when we pay attention 
to the fact, that the stages of development hitherto stated distinguish 
themselves, with only one exception, by only one phenomenon of 
transformation that can be indicated in the formula. The distance 
between each other of these stages of development is consequently 
in a morphological sense the same. 
This is the case with the stages Jf to /la and //e to ILIb. 
If however we compare the forms //a and J//c, we see that in 
the latter two phenomena of transformation are present, namely 
a transformation of the 25' vertebra into a first sacral vertebra, 
and of the 20'" vertebra into a dorsolumbal vertebra. 
The distance between these two forms is consequently greater 
than between the others. This suggests the supposition, that between 
the stages Jia and //c a stage might exist, characterized by the 
fact that the 25% vertebra has already become a sacral vertebra, 
whilst the 20'' vertebra has still remained the last dorsal vertebra. 
To this answers a formula //b, which I have inserted into the 
series provisionally as an hypothetical one. I have in vain looked for 
such a form among the 100 vertebral columns under consideration. 
When studying the specimens, which Ll am collecting for the second 
hundred, | have however found the designated form of the vertebral 
column and even three times. 
The formula //6 is therefore no longer an hypothetical one, 
