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coidemii in ^oullifiil slfidia does not show a single trace of the 

 fenestra |)rinci|ialis, and the region of the later incisnra scapulo- 

 procoraroidea slill forms pari of tlie homogeneous compact fornialioii 

 of the scapnlo-coracoi<letim. When later a progressive histological 

 differentiation occurs at the place wiiere scapula, coracoidenm s. str., 

 epicoracoid and procoracoid Avill originate (formation of cartilage) 

 this is ac.C(nnpanied by regressive changes al the plai'e of the fenestra 

 |)i'incipalis and of tiie incisni'a scapnlo-coracoidea, vi/-. a thinning of 

 the hlastema and tinally reduclion to a thin membrane of connective 

 tissue. The ci-anial closing of the incisnra does not occupy such a 

 [)rominent i)lace in llies(! regi-essive changes. In the lig. scapnlo- 

 procoracoidenm there arc slill cartilaginons insulae in llie oldest 

 embryos, which prove that lliis ligament is a reduced portion of 

 the coracoid (in a wider sense). In fig. 5 Ihe four schemata show 

 the process of development of the coracoi<lenm. The scapular end 

 of the clavicle has not been hatched in each of the figures, and has 

 been indicated in the same form. In ihe primary girdle halching 

 indicates blastema, praechoudrium or connective tissue according as 

 the halching is more or less close. Entire absence of halching indicates 

 cartilage. The ab origine present ner\e-canal has l)een omilled. Tlie 

 figures require no fnrlher explaiuxlion. Thus genelically both the 

 fenestra principalis and the incisnra scapnlo-coracoidea, i.e. the 

 membranes which enclose them, are parts of the shonlder-girdle. 

 The lig. scapulo-coracoideum is, as it were, a reduced procoracoid. 



As regards the episteiiium, in the youngest embryo in which a 

 blastemalic clavicular [irocess was found, il was conlinnous with 

 the primary shoulder-girdle. From which 1 deduce a genetic con- 

 necliou, in a sense that Ihe clavicular blastema originates as a process 

 of the scapulo-coracoid. It might slill be op|)osed that Ihe stadium 

 in which this connection did not yet exist has nol come into n)y 

 hands, to which I might return that the bone in the blastemalic 

 clavicula first occurs dorsally and enlarges in a ventral direction, 

 a symplom which, in my opinion, is strongly in favour of Ihe genesis 

 of the clavicula as a process of the scapulo-coracoideum. 



The further development of ihe clavicular blastema I shall describe 

 shortly with the help of fig. B. In illustralion a, already a faii'ly 

 large bony clavicula is seen to be present in llie blaslemic clavicular 

 process. In illustralion h this is not more Ihan a strip of bone lying 

 in the cranial border of a large, for the rest homogeneous, blastema. 

 In illustration c a further diflferenlialion in Ihe said blastema has 

 commenced. It consists now of a cenlrum poorer in cells and a 

 denser meseuchymalous border. In the latter, which represents a 



