24 



comes (o insertion al tlie clavicula. Finally, tlie medial boundafj 

 forms a blastema strip, in which llie half of the little cranial |>oint 

 of the episteninm will develop later. The complex of clavicular and 

 episteriial formations is connected with that of the oilier half of the 

 body at (he level of clavicle and episteriial iransverse bar; the 

 caudal processes are still separated. 



Embryo Lacerta ag. P. (N. T. al)out 33). In this embryo the 

 sternal borders are already blended cranially. Apart fro?Ti a com- 

 mencement of calcifying cartilage, (here is nothing to remark at 

 the primary shoulder-girdle except (he occurrence of a cai'(ilaginous 

 itisula in the lig. scapulo-procoracoideuin. The coracoidea have 

 passed the medial line, and are thus pardy overla])ping each other. 

 The ceniral IhiuuiMg in the episierno-clavicular blastema has com- 

 ple(ely given place to the membrana-clavicularis. In (he caudal 

 liorder the episternal (raiis\erse bar has elongated, and its lateral 

 e.xiremity is at(aciied by ligament to the clavicula. The episternum, 

 now grown unpaired, has also accjuired a cranial poin( which inter- 

 poses itself between the two clavicles. In cross-sections it shows 

 traces of paired formation, (deep medial groove on I he dorsal side); 

 the paired bony formation I have no( seen however. On the medial 

 half of the t'lavicula a thick cranial border and a thinner caudal 

 bone-plate can be distinguished, the latter being evidently an ossified 

 portion of the claviculo-episternal membrane. 



In embryo Lacerta ag. Q. (N.T. about 33 — 34) the cranio-caudal 

 measurement of the episternum has attained i(s definite relative size. 

 Several cross-sections show a paired cranial episternal point. This 

 duality is merely local however. Nevertheless I take it as a proof 

 that also this part of the episternum is formed pairedly, in which 

 case the whole bony episternum was originally paired. In the primary 

 shoulder-girdle the calcification has extended. 



Regarding embryo Lacerta ag. R. (N.T. about 34 — 35), in which 

 tiie portions of the bony skeleton discussed here have all attained 

 their definite form, altiiough on a small scale, there is nothing of 

 note except that in the lig. .scapulo-|)rocüracoidenm vestiges of 

 cartilage are still to be found. 



When the scapulo-coracoideum passes into praecliondrium and 

 later into cartilage, a narrow strip of tissue remains between it and 

 the bony clavicula at the blastema stage. We can now for the first 

 time speak of a syndesmosis scapulo-clavicularis, although the 

 connection between scapula and clavicula was already long present. 

 Only with the histological differentiation of the scapulo-coracoideum 

 is it possible to indicate the boundary region as syndesmosis. 



