. Text-book of embryology. Embryology. n. B. nc Fig. 136.âTransverse sections showing various stages in the development of the opisthonephros. (After Furbringer, â 1877.) A, Triton alpestris ; B, Salamandra maculata, 14 mm. ; C, D, Salamandra maculata, 17 mm. ; JE, SalamandranuKulata, 21 mm.; F, Salamandra m,aculata, 25 mm. A, dorsal aorta; , archinephric duct; g, gonad ; gl, glomerulus ; n, nephrotome; nc, nephrocoele ; , rudiment of peritoneal canal; splc, splanchnocoele; t, tubule; Z1, t2, $, primary, secondary, and tertiary tubule rudiments. coils and windings as it does so (Fig. 1
. Text-book of embryology. Embryology. n. B. nc Fig. 136.âTransverse sections showing various stages in the development of the opisthonephros. (After Furbringer, â 1877.) A, Triton alpestris ; B, Salamandra maculata, 14 mm. ; C, D, Salamandra maculata, 17 mm. ; JE, SalamandranuKulata, 21 mm.; F, Salamandra m,aculata, 25 mm. A, dorsal aorta; , archinephric duct; g, gonad ; gl, glomerulus ; n, nephrotome; nc, nephrocoele ; , rudiment of peritoneal canal; splc, splanchnocoele; t, tubule; Z1, t2, $, primary, secondary, and tertiary tubule rudiments. coils and windings as it does so (Fig. 136, E) while the Malpighian body dilates and its dorsal wall becomes invaginated to form the glomerulus. As a rule the primitive con- tinuity of nephrotome with the splanchnocoelic lining disappears in the Amphibian as already indi- cated, but it becomes re-established by a peritoneal canal developing secondarily (Fig. 136, D) as an out- growth, arising in Urodeles usually from the neck of the Malpighian body and in Anura from a point farther down the apparent tubule, which grows towards and fuses with a thickening of the coelomic epithelium. Such displacements of the communication between Mal- pighian coelome and splanchnocoele are probably of a similar nature to those mentioned in the case of the pronephros of ITypogeophis (see p. 226). In those parts of the opistho- nephros which are actively renal in function, the hinder portion in Urodeles and the greater part of the whole length in Anura, there takes place great increase in bulk, associated with the development of generations of subsequent tubules. Such secondary, tertiary, etc. tubules make their appearance amongst the mesenchyme in the form of cellular strands which resemble closely â both in their original appearance and in the series of changes which they pass through âthose from which the primary elements arise (Fig. 136, F, t3). Eventually the secondary tubule comes to open into the primary tubule, the term
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