220 THE ROYAL SOCIETY OF CANADA 



second joints. This seta was not present on the other specimen 

 which was exuviating to stage VI, nor is it figured by Sars. 



Three specimens of M. longa stage V occurred ; two females and 

 one male, 3-5, 3, and 3 mm. The p5 of both sexes were much larger 

 than those of M. lucens, and four jointed, the first three joints similar 

 in appearance and size. The third joint of the female carried distally 

 a short slender outer seta; the terminal joint was about equal in 

 length to the third and carried three long slender setœ (Fig. 57). 

 The third joint of the male carried distally a very small outer seta; 

 the terminal joint was nearly 43^ times as long as the third joint, 

 with two small outer setae, two terminal setse and four small inner 

 setae (Fig. 58). 



In conclusion I wish to acknowledge the kindness and assistance 

 which I received from my professor, Dr. Willey. 



Explanation of the Figures 



Fig. 1. C. finmarchicus V exuviating to VI. Part of outer ramus of fifth foot, 

 showing terminal and external setse withdrawn into seta sacs. 



Fig. 2. Same. Caudal ramus with inner cylinders of terminal setae of exuvia ex- 

 posed, cylinders and seta sacs formed by everting setse. 



Fig. 2} Same. Seta of exuvia slipping off inner cylinder. 



Fig. 3. Same. Terminal setse of caudal ramus unfolding. 



Fig. 3.' Same. The new third terminal seta of the right caudal ramus with inner 



cylinder formed at base. 

 Fig. 4. C. finmarchicus V. Urosome showing regeneration of lost setse. 

 Fig. 5. C. hyperboreus\\\-W. 



Fig. 5.^ Mandible; inner lobe (molar process) withdrawing. 

 Fig. 5.- Maxilla; first inner lobe (Li I) withdrawing. 



Figs. 6 to 19. C. finmarchicus IV. Variations of coxal teeth on the fifth feet. 

 The lengths in millimetres were (6) 2-017; (7) 2-00; (8) 2-00; (9) 2-10; 

 (10) 2-06; (11) 2-13; (12) 2-12; (13) 2-18; (14) 2-26; (15) 2-60; (16) 

 2-80; (17) 3-06; (18) 3-08; (19) 2-84. 

 Fig. 20. C. finmarchicus IV-V. Fifth foot showing internal coxal teeth of stage IV; 

 also internal segmentation of Re and Ri. 

 C. finmarchicus IV-V. Coxal teeth of p5, external and internal. 

 C. finmarchicus IV-V. A caudal ramus. 

 C. finmarchicus V. Bl of p5, aberrant. 



C. finmarchicus V-VI. Bl of p5 showing external and internal coxal teeth. 

 C. finmarchicus V-VI. Bl ot p5 showing external and internal coxal teeth. 

 C. finmarchicus V-VI. Caudal ramus showing wrinkled bases of seta 

 sacs. 

 Fig. 27 A. C. finmarchicus V-VI. Urosome. 

 Fig. 27 B. C. finmarchicus. Outer aspect of new caudal ramus. 

 Fig. 28. C. finmarchicus V-VI. External and internal coxal teeth. 

 Fig. 29. C. finmarchicus V-VI. External and internal coxal teeth. 

 Fig. 30. C. finmarchicus V-V\. Exuviation of urosome. 



