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the sternal formation has not been lengthened past the fourth rib 
in the direction of the fifth. | think I have to conclude from this 
that the autochthonic sternal formation does not reach further cau- 
dally than up to the insertion of the fourth rib. The two sternal 
bands in this embryo have come cranially within a very short 
distance of each other. Neither here nor in any of the younger 
embryos there could be observed anything like a median formation 
that was also to grow into one whole with the sternum. Still the 
sternal ridges are here found immediately before the beginning of 
the growing together in the median line, as appears from the following 
embryo. 
I found a somewhat older stage in the embryo Lacerta ag. Q. 
(N. T. about 33). The sternal bands, which here were cartilaginous, 
had already fused in the most cranial part. Caudally to the later 
breastbone-fontanel as yet no joining had taken place in the median 
line. All five ribs were joined by means of cartilage to the sternum, 
which was also cartilaginous; so they formed together one large 
continuum of cartilage. Moreover the syndesmoses are wanting, which 
in the adult lizard separate the xiphisterna from the prosternum. 
In the embryo Lacerta ag. Q. (N. T. ab. 33—34) the sternal 
bands have fused cranially, as in embryo P; then follows the region 
of the breastbone-fontanel; still more caudally, on a level with the 
insertion of the third rib, the sternal bands are again situated close 
to each other. A thin layer of blastema proves that no fusion has 
as yet taken place here. Caudally to this part the sternal ridges 
diverge, never to reach each other again (c.f. diagr. 1). 
Still completer is the fusion of the sternal bands in embryo 
Lacerta ag. R (N. T. ab. 34—35), while in embryo Q there was 
only a blastematic connection in the median line, in embryo R a 
cartilaginous connection is formed caudally to the fontanel. Moreover 
the two xiphisterna have joined on the level of the fifth rib. So in 
this embryo, the oldest examined by me, the adult form has been 
reached, at least in the main. A difference is still formed by the 
absence of all syndesmoses. They have to be formed secondarily in 
places where cartilage existed first. Therefore these syndesmoses 
have no morphological value; they are not lines of division to 
which, strictly taken, any importance may be attached. They have 
only a mechanical importance. 
Of Gongylus occellatus I had eleven embryos at my disposal. 
Older stages, like the embryos P, Q and R of lacerta were wanting. 
Neither did I possess an adult specimen, nor an image of the adult 
sternal apparatus. So I can only give a few data established in 
