98 KARM NARAYAN BAHL 



body-wall, restoring the coelomic cavity on the dorsal side. 

 I did not meet with much success even by this method. At 

 last I was lucky in finding two embryos, one of which was just 

 of the right age (about 6 mm.) and in both of which the gut 

 was narrow and the coelomic cavity all round very spacious. 

 A complete series of longitudinal sections of one of them gave 

 me all the stages of development of the septal nephridia, and 

 I was able to establish, firstly, that the septal nephridia 

 develop between the two peritoneal sheets (inter-peritoneal), 

 and, S(!Condly, that they could be traced to their final septal 

 position from their first place of origin in the primary nephric 

 row in the body-wall. 



12. Summary. 



1. The three kinds of nephridia — integumentary, septal, 

 and pharyngeal — appear at successive stages of development 

 of the embryo ; the integumentary preceding the septal and 

 pharyngeal, both of which develop simultaneously. 



2. All the three kinds can be traced back to the original 

 row of nephridial cells of ectodermal origin. Thus all the 

 different nephridia are ultimately derived from one common 

 origin. 



3. The primary pair of integumentary nephridia are the first 

 to appear from a ' retro-peritoneal ' group of cells. The 

 rudiments lack the ' funnel-cell ', and consequently a ' coelomic ' 

 funnel is never developed in these nephridia. They open to 

 the exterior on the body-wall. 



4. These primary integumentary nephridia do not appear 

 in the same position in successive segments of the embryo, 

 but are irregularlv distributed all over the bodv-wall. 



5. The septal primary nephridia can be traced back to a group 

 of nephridial cells, including the ' fumiel-cell ', which make 

 their way into each septum between its two adjoining peri- 

 toneal lamellae. 



6. The primary septal nephridia have always a well-developed 

 pre-septal funnel, and appear along a straight line on both 

 sides of the dorsal vessel. They appear after the primary 



