225 
The next stage is represented by the embryos Lacerta ag. E and 
F (N.T. about 26), which show nearly the same stage of develop- 
ment. The outline of the shoulder girdle has become clearer. The 
coracoidal and the scapular part can very well be recognized. In 
aA, > 
SVN | Ty 
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2e Ab 
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tes 
vate 
„le 
EN 
TE oe 2 q 
RE i 
Er ee ew 
Fig. 2. Lacerta agilis S. transversal. 
the humeral diaphysis praechondrium is found. In comparison with 
embryo D there is a further progress in the increased size of sternum 
and shoulder girdle. Sternum and shoulder girdle have grown in each 
other's direction. This has caused the layer of undensened mesen- 
chyme, ab origine found between them, to become less clear. 
A considerable progress in development may be stated in the 
embryo Lacerta ag. I (N.T. about 28). In the humerus we here find 
for the first time cartilage. In their further growth sternum and 
coracoideum have come so near to each other that they appear 
together in transversal sections. It has become almost impossible to 
outline them clearly with respect to each other. In the accompanying 
diagram we see an only slightly lighter zone of partition. If the 
embryos described above had not been examined, the sternum would, 
on the ground of this embryo, certainly have been declared to be 
a product of the coracoideum, and this stage would have been 
interpreted as the first stage of the sternum being cut off its matrix, 
the coracoideum. The ribs have approached the sternal formation 
