Plate II. 

 Fig. 5. Dorsal aspect of adult 5 CJia-toptenis. (From preserved specimen.) 

 X %• 

 Fig. G. Ventral aspect of same specimen, x %• 



Fig. 7. Model of accessory feeding-organ of the 13th segment. X 3. 



Fig. S. Posterior aspect of partially dis.sected sexual segment of advilt 

 Cha'toptcriis. Ventral side uppermost, x !%■ 



Fig. 9. Ventral aspect of larva of (JJiaiopteriis. (Drawn from life.) 

 Six days old. 1 mm. long, x "^3- 



Fig. 10. Ventral aspect of larva of CIi at opt eras at beginning of the trans- 

 formation. (Drawn from life.) 1.5 mm. long, x 31. 



Fig. 11. Ventral aspect of larva of Chcetopterus at the time of the trans- 

 formation from free-swimming to creeping stage. (Drawn from life.) 2 mm. 

 long. X 23. 



Fig. 12. Same larva. Dorsal aspect. Post-oral lobe extended, x 23. 



Fig. 13. Same larva. Viewed from left side. Post-oral lobe depressed. 

 X 23. 



Fig. 14. Posterior end of adult Glurtopterus. Shows regeneration of the 

 sexual segments. X 5- 



