DEVELOPMENT OF NEPHRIDIA OF PHERETIMA tOl 



EXPLANATION OF PLATES 5-7. 



Illustrating Dr. K. N. Bahl's paper ' On the Development of 

 the " Enteronephric " type of Nephridial System found in 

 Indian Earthworms of the genus Pheretima'. 



Fig. 1. — Whole mount of a very young embryo (146/i X 130ju) seen in 

 a ventro-lateral aspect, showing the mesodermal pole-cell m.p.c, the 

 neural and nephridial teloblasts n.n.t., and the mesoderm band ')n.b. 

 x500. 



Fig. 2. — Longitudinal section of an embryo 245pi in length, showing the 

 relative position of the mesodermal pole-cell and one of the teloblasts. 

 The ectodermal origin of the teloblast is clearly indicated. T, the neural 

 teloblast ; ex., coelomic cavities in the mesoderm ; arch., archenteric 

 cavity ; end., endodermal cells with yolk-granules, x 500. 



Fig. 3. — Ventral portion of a transverse section from the posterior end 

 of an embryo 300/x long, showing the origin of the teloblasts in the ecto- 

 derm. The teloblasts are still embedded in the ectodermal layer, but are 

 sharply marked off from the definitive ectodermal cells. On the right are 

 seen two teloblasts, the ventral one being the neural and the lateral one 

 the nephridial. On the left are seen three cells still embedded in the 

 ectoderm which lie in front of the teloblasts and have been budded off 

 from them, n.t., neural teloblast ; np.t., nephridial teloblast ; c.L, cells 

 budded off from teloblasts ; m.s., hollow mesodermal somites with coelomic 

 cavities, c.c. ; ect., ectodermal cell, x cir. 620. 



Fig. 4. — Ventral portion of the section just in front of the one shown 

 in fig. 3, showing the gradual demarcation of the neural and nephridial 

 cells from the definitive ectoderm, lat.t., lateral teloblast ; n.c, neural 

 cells ; nph.c, nephridial cells, x cir. 664. 



Fig. 5. — Ventral portion of a longitudinal section through the hind end 

 of an embryo about 3 mm. long, showing the nephridial string of cells 

 breaking into the cell-masses destined to give rise to the nephridia. 

 M.P.C, position of mesodermal pole-cell; nph.t., nephridial teloblast; 

 nph.l., nephridial layer of cells ; }ii.l., layer of mesoderm with coelomic 

 cavities; ed., ectoderm. x545. 



Fig. 6. — Transverse sections of an embryo 300/x long, from which 

 figs. 3 and 4 have been drawn, showing the ' funnel- cells ' in section 

 between the two adjoining coelomic cavities, i.e. in the septa, n.c, nerve- 

 cord ; nph.c, groups of nephridial cells ; f.c, funnel-cells ; ect., ectoderm. 

 X400. 



Fig. 7. — Portion of a longitudinal section of an embryo, showing the 

 nephridial groups of cells pushing into the intersegmental septa. Other 

 letters as before, x 640. 



