The material consists of 7 human embryos which lengths range from 20mm to 16cm, inserting 22, 2 7, 35, 40 and 55mm long specimens between them. The youngest 20mm long embryo belongs to the Streeter's horizon XVIII developmental stage, in which three semicircular ducts and all the peripheral nerves to the sensory epithelium of the membranous labyrinth are distinct. Its otic capsule is cartilageous only in its vestibular part, its cochlear part remains precartilageous.
In the next 22mm long embryo the cochlear part becomes also cartilageous, though not so much advanced as the vestibular part, and the fenestra perilymphatica becomes distinct which is in the previous stage of 20mm long specimens already only as a less dense area from the surrounding precartilageous tissue discernible (Fig. 1, 2, 3, Pl. 1)
In this 22 and next 27mm long specimens the histological appearance of the medial and lateral margin of the fenestra perilymphatica is not the same. The surface of the lateral margin shows a dense mesenchymal layer, while that of the medial not.(Fig 4-5 Pl. 1)
In the next 35mm long specimen appears a little fibrous characteristic in this dense mesenchymal layer of the lateral margin so that two fibrous layers in the opening radiating from the lateral margin medialward becomes distinct. These two layers in the opening have a less dense layer between them. The inner layer among the two is direct under the cochlear duct, the outer one continues medialward to that area, where canaliculus cochleae appears. These structures in 35mm long become more distinct in 40mm long one.(Fig. 9, Pl. 2, Fig. 15, Pl. 3)
Streeter's periotic space begins to form already in 35mm long specimen and it becomes spacious neighbering fenestra vestibuli in the next 40mm long. But the space of the scala tympani is not yet to be seen, its spacious structure appears only in the next 55mm long specimen. In the latter not only the scala tympani, but also the scala vestibuli is very spacious in comparison with the cochlear duct.
In the region of the fenestra perilymphatica is formed the cartilageous canaliculus cochleae, although very short, in this 55mm long embryo.Such formation of cartilageous canal begins already in 35mm long one, in which only as a cartilageous protrusion (Fig. 6-9, Pl 2*), in the next 40mm long one in the form of a cartilageous process (Fig. 11, Pl. 2, Fig. 11-14, Pl. 3*) under the mesenchymal anlage of the canaliculus (Fig. 9, Pl. 2, Fig. 15, Pl. 3°) from behind foreward. This cartilageous process may fuse with the cochlear part and make a canal.(Fig. 18-23, Pl. 4, Fig. 24-26, Pl. 5)
This cartilageous canal of the canaliculus becomes long and covers almost all length of the mesenchymal aquaeductus canal in 16cm long embryo (Fig. 27-35, Pl. 5-6) As the cartilageous tube of this canal reaches near the scala tympani in this specimen, there appears a cartilageous process protruding to this end of the tube, This cartilageous process makes a new hinder rand of the fenestra cochleae and coming near the tympanic end of the canaliculus tube it does not fuse with the latter so that there remains a very narrow mesenchymal part which connects the two part canaliculus and fenestra cochleae. The same structure is also in the osseous capsule observable.
The mesenchymal canaliculus begins to be formed. in 40mm long one as a continuation from the endocranial dural layer before the gangl. sup. of the glossopharyngeal nerve to the outer fibrous layer of the opening of the fenestra perilymphatica. This fibrous strand becomes in the next stage of 55mm long one a tube with fibrous wall, in which lumen there is some reticular structure. Such structure does not change in 16cm long one, its wall becomes thicker, its surrounding mesenchym is not so loose as that of the fenestra cochleae.
The existence of the Waltner's barrier membrane is doubtful.

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The material employed consists of 9 human embryos which range from 4.5 to 20mm length and belong to the Streeter's 5 developmental stages horizon XIV-XVIII. The beginning of the metanephros is observed in 4.5mm long embryo, which belongs to the horizon XIV. It appears as a form of 95μ long so-called Nierengang and projects dorsal and cranial from the dorsal and a little medial wall of the Wolffian duct 133μ cranial from the opening to the cloaca. The metanephric tissue layer is already in contact with the cranial end of this ureterir bud.
In the next stage of horizon XV, to which belong 6mm (K) and 10mm (F) long specimens, the cranial end of the ureteric bud enlarges and becomes the pelvic portion, while the rest part remains ureter; the length of the latter is 190μ on both sides in these 2 specimens. The metanephric tissue of the enlarged pelvic portion differentiates in two layers; the inner layer contacts with the pelvic portion, the outer covers this inner layer.
In 7.5mm long embryo of the horizon XVI the pelvic portion enlarges craniocaudal two-fold to the preceeding stage and differentiates into cranial and caudal portions which may correspond to the two future major calyces. These two cranial and caudal portions are covered with the inner layer of the metanephric tissue respectively, the intermediate portion between these two only with the outer layer directly, so that the inner layer is separated into two cranial and caudal portions. Its ureter is 323μlong on the right, 285μ long on the left.
To the next horizon XVII belonging embryos are 9.5mm, 10mm (U), and 14mm long. By the former 2 earlier specimens comes the opening of the Wolffian duct to the cloaca near that of the ureter; that portion of the Wolffian duct caudal to the opening of the ureter seems to become the wall of the cloaca. The pelvic portions of these specimens situate cranial to A. iliaca communis. The length of the ureter is 835 in 10mm (U) long one on both sides. In the pelvic portion there appear except cranial and caudal divisions two ventral and one dorsal so that there are 5 divisions on both sides of 9.5mm long one, while they are in 10mm (U) long one 6 (ventral and dorsal each 2) on the right, 7 (ventral 2 and dorsal 3) on the left side to be observed. The number of these di visions becomes 10 in elder 3 specimens, 14mm-(late XVII stage), 18mm (a) and 20mm (XVIII stage) long ones. In these specimens there are except cranial and caudal always 4 ventral and 4 dorsal divisions, and they correspond to the Felix's collecting tubules of a first generation The collecting tubules of a second generation begins to form only at the caudal division on both sides of 10mm (U) long specimen. Such subdivision increases in 14mm long one, 9 among 10 on the right, 8 on the left, but there is no subdivision of a third generation. The latter occurs 5 among 10 on the left, 4 on the right in 18mm (a) long embryo. There is not yet subdivisions of a fourth generation. The latter appears in 20mm long embryo 4 among 10 on the right side, 2 on the left. By this specimen there is no primary division already, the subdivision of a second generation 2 on both sides, that of a third generation 4 on the right, 6 on the left. These subdivisions progress always dichotomic.

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