232 
In the embryo Ptychoz. hom. A we find a very early stage. A 
blastematic paired sternal formation, unconnected with any other 
skeleton-formation, is found in the lateral trunk-wall. 
RL 3 aa, 1 Nene 
~ x a 1 ele 
neueniiny,’\ ay EN 
. 
IN 
t 
7 
1 
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. 
1 
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—t este esin 
H appar 
Fig. 6. Gongylus ocell. L. frontal. 
If one sees the smallness of the ribs, and that in the humerus 
no cartilage is as yet present, one may conclude that the maximal 
approach of sternum and coracoideum has not been reached by a 
long way, in other words that the zone of division does not represent 
the formation of the articular cavity. So this embryo corresponds 
on the whole with embryo S. of lacerta. 
The embryo Ptychoz. hom. B is much older. On both sides one 
finds a sternal formation to which three ribs have been joined. 
In the preceding words my experiences in studying some thirty 
embryos were rendered separately. We shall now consider what 
conclusions they enable us to draw. 
In the first place: the youngest formation of the sternum is paired 
and autochthonic; in so far I quite agree with BoGorsosski. If one 
has come to this conclusion, one has to ask oneself this question: 
What part of the definite thorax-skeleton was formed out of this 
