299 



3°. There is no indication of a spina scapniae. Tlie margo superior 

 is neither ihickeiied nor split into two labia. 



Fig. 1. 



Fig. 2. 



4°. The margo superior is .straight, so there is no incisiira .scapulae. 



5°. For the rest the shape of the scapula fairly well agrees with 

 that of an adult .shoulder-blade. In reconstructing the scapulae of two 

 monkey embryos (viz. Macacus cynomolgus 17 mm. in lenglli, and 

 Semnopithecus maurus) it became evident that, also in these primates, 

 the embryonic shoulder-blade already in its first beginning resembles 

 that of the adult. Here also a .spina was absent. 



6°. Close beneath the angulus superioi- we observe a well-detlned 

 fovea where a foramen is found in older stages of development. To 

 this we shall rever't when discussing the following stage. 



This stage is illustrated in fig. 2. It concerns the shoulder-blade 

 of an embryo, 25 mm. in length. Also in this stage any indication 

 of a spina scapulae or of a thickening of the margo superior is 

 lacking. Nevertheless when compared with the first stage some 

 modifications can be recognized. 



IV The shoulder-blade does not lie any more in a sagittal plane, 

 but makes an angle with it, as is also the case with the adult. The 

 joint-cavity lies at the level of the first rib. Acromion and clavicula 

 have joined. 



20 



Proceedings Royal Acad. Amsterdam. Vol. XXVI. 



