ASPLANCHNA EBBESBORNII (rOTIFER) 



413 



dorsal posterior end (text fig. r and fig. 98) . The urinary bladder 

 (pulsating vacuole) is formed by an evagination and enlargement 

 of the inner end of this invagination (text figs, s and t). The 

 walls of the urogenital sinus on either side, in its early differen- 

 tiation, fuse with the posterior ends of the group of cells which 

 form the excretory rudiments (text figs, r and s), and finally a 

 direct communication is established between the pulsating 



Fig. s Horizontal section of embryo, to show fomration of the excretory 

 system, tags, urogenital sinus, and bladder. 



Fig. t Median longitudinal section, to show the relation of parts. 



Fig. u Completely formed excretory tubules from the right side of embryo 

 at the time of birth. 



ABBREVIATIONS 



bl, bladder 



br, brain 



b.w., body wall 



c, cilia 



d.g., digestive glands 



ft, foot 



k.t., kidney tubules 



lu, lumen 



oe, oesophagus 



ov, ovary 



r.t., recurrent tubules 



st. stomach 



ta, tags (flame cells) 



u, uterus 



vt, vitellarium 



