EXPLANATION OF PLATE XIII. 



Fig. I. — Young zooecium of Paludicella ehrenbergi, X 30. 



,, 2. — Two zooecia of PoUsiella ereda, in one of which the poly- 

 pi de is undergoing regeneration, X 30; 2a, alimentary 

 canal, funiculi and immature gonads of the other 

 polypide, X 75 (only the upper part of the testis is 

 shown). 



J, 3. — Young adult zooecium of Victor ella bengalensis with a 

 single distal bud commencing to develop , X 30. 



J J 4. — Tip of an adult zooecium of Vidorella mulleri, X 75. 



^, 5. — Tip of an adult zooecium of Vidorella pavida, X 75. 



,, 6. — Lateral view of the upper part of the stomach and the 

 adjacent parts of the alimentary canal in Vidorella 

 symhiotica , with the cardiac compressor muscle re- 

 laxed, X 240. (The polypide is slightly macerated 

 and the chitinous lining of the oval chamber shows 

 very clearly.) 



J, 7. — Dorsal view of cardiac part of the stomach, etc., in 

 V. bengalensis, with the cardiac compressor con- 

 tracted, X 240. 



,, 8. — Distal part of a zooecium of V. bengalensis containing a 

 recently regenerated polypide, X 75; to show the 

 simple structure of the alimentary canal at this stage. 



,, 9. — Lateral view of a zooecium of Hislopia lacustris growing 

 in a confined space, X 75. The zooecium is much 

 higher and narrower than usual. 



,, 10. — Alimentary canal of Hislopia lacustris from the dorsal 

 surface, X 75. 



,, II. — Wall of the crop of Hislopia as seen in optical section 

 from above, with green cysts, X 240; to show the 

 two cellular layers and the inner chitinous coat. 



,, 12.- — Dorsal view of the gizzard of Bowerbankia caudata and 

 the adjacent parts of the alimentary canal, X 75. 



,, 13. — Gizzard of the same polypide in optical section, X 240. 

 (In both figures a diatom grasped by the teeth of the 

 gizzard is shown.) 



a = oesophagus; 6 = chamber lined with chitin; c = cardiac 

 chamber of the stomach ; d = pylorus ; e = intestine ; / = rectum ; 

 g = cardia or cardiac valve ; h = cardiac compressor muscle ; ni == 

 green cysts ; n = orifice of the zooecium ; = retractor muscles ; 

 r = parietal muscles ; x = base of lateral bud ; z = distal bud. 



