91 
specimens form a morphological progression, demonstrating a beginning 
of the reduction of the 12 pair of ribs. 
At the same time it is very clear that these three specimens cannot 
be directly derived the one from the other, that consequently they 
do not form what might be called a descensional succession. 
This shows the 24 vertebra. In specimen 1 the contact with the 
sacrum has been formed on the right side of the body, in the two 
other specimens on the left side. These three specimens consequently 
belong at least to two successions that have diverged, be it only in 
a slight degree. 
And if in the specimens 2 and 3 we carefully examiae the pars 
lateralis, then it appears from observations, which we cannot enter 
into particulars upon here, that the specimen 3 which, with regard 
to the twelfth pair of ribs, is higher developed than the specimen 2, 
is, with regard to the facies auricularis, more primitive than the 
specimen 2. Thus, likewise between these two specimens, there exists 
a slight divergence of development. All three specimens are conse- 
quently the extremities of three independent progressions of develop- 
ment, though they may be only very short. 
As a second and last example the two specimens representing the 
stage ///b may serve. 
We see that the reduction of the 12 pair of ribs has reached a 
higher degree; in the specimen 2 these ribs are already so little 
that they look much like much reduced 13 ribs. Together with 
„the specimens of the stage ///a these two specimens exhibit, in the 
most convincing manner, the gradual reduction of the 12" pair of ribs. 
The 24% vertebra is in the stage ///b first sacral vertebra, and 
it is obvious that, in specimen 1, it is transformed in a slighter 
degree than in specimen 2. 
With regard to these points (I leave other points out of discussion) 
specimen 2 is doubtless the higher developed one. That this specimen 
does not after all directly continue the line of development of spe- 
cimen 1, but deviates from it divergently, appears from the position 
of the facies auricularis, which in specimen 2 is a less transformed 
one than in specimen 1. This is likewise seen, when considering 
the 30 vertebra. In specimen 2 this vertebra has still cornua coc- 
cygea, whereas these have already almost completely disappeared in 
specimen 1. This points likewise ‘to divergent development. 
This divergency of development is shown by all specimens belonging 
to any stage. It is however so slight that the specimens remain un- 
mistakably within the boundaries of the separate stages. 
It is however of importance to ascertain this divergency, because 
