252 EMBRYOLOGY OF THE LOWER VERTEBRATES CH. 



n 



and 

 *plc. 



}'.ji'>. Transverse sections showing 

 various staffs in the development of 

 the OpictbooephroC. (After FurLiin^-i, 



1877.) 







14 MIDI 'lulu. 17 MUM. ; 



I 'inn ml ni 



Mrrlun.-j.lnic d n:il ; <//, ^""I'-mlus ; 



. ii'|.liinioiin- ; /<-. iifpliHM-Mi-li- ; /i.< . i mlimiMit 

 '.ni-al I-;IM:I| ; >/,//-, sjilaiiHn.'.rc .<-|i- ; /. 

 tMl.nl.-; n, I'-i, /:(, pin,,., 



lllljlll.- Illiir 



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 Hypogeophis (see p. 

 226). 



In those parts of the opistho- 

 nephros which are actively renal in 

 function, i.e. 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 both in their original 

 appearance and in the series of 

 changes which they ja.ss through 

 those from which the primary 

 dm, cuts arise (Fig. 136, F, / ; ). 

 Kyentiially the secondary tubule 

 comes to open into the primary 

 luluilc. I In- terminal section of which 

 MHIS I'nnns a collecting- 1 ul>f com- 

 mon t<> both, while Mie tertiary 

 tubule .similarly comes (<> oj.eii into 



