312 CHARLES ALBERT SHULL. 



EXPLANATION OF PLATE I. 



All figures except Fig. 17 are X 5- 



FIG. I. Second right pleiopod of C. virilis Hagen, 9 showing two supernumerary 

 appendages. 



FIG. 2. First right pleiopod of the same specimen. 



FIG. 3. Third right pleiopod of C. virilis, $ , modified for sexual purposes. 



FIGS. 4-7. Successive steps in the regeneration of the fifth right pleiopod in 6. 

 (Bartonius) bartoni, 9- 



FIG. 8. Left pleiopod from same somite as Fig. 7, without regeneration, drawn to 

 same scale. 



FIG. 9. Fourth left pleiopod of young C. (Bartonius) bartoni, 9> a ft er two 

 moults. 



FIG. 10. Fourth left pleiopod of older C. (Bartonius} bartoni, 9, after three and 

 one half months. 



FIG. ii. Third right pleiopod of C. (Bartonius} bartoni, $ , after one moult. 



FIGS. 12-13. Second left pleiopod of C. (Bartonius} bartoni, 9, condition im- 

 mediately after amputation, and after the second moult. 



FIGS. 14-16. Right uropod of C. (Barlonius} bartoni, $, conditional amputa- 

 tion, before, and after, second ecdysis. 



FIG. 17. Diagram illustrating the way in which the abnormal appendages shown 

 in Figs. I and 2 may have been produced. 



