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ANDREWS. 



EXPLANATION OF PLATE II. 



FlG. 7. Section of ovary of D. cuprea. s, septum; v, blood-vessel; ov, enlarged 

 cell forming an ovum; a, cluster of small nuclei around a capillary; b, linear arrange- 

 ment of nuclei; c, cell string not yet free from matrix. Camera, Zeiss. 2. F. 



Fig. 8. Three successive stages in the formation of spermatozoa in D. magna, 

 a, small group of cells first liberated from testis ; b, mass resulting from division and 

 growth of a; c, final product of one-half of group b. Camera, Zeiss. 4. F. 



Fig. 9. Ripe, active spermatozoa. Camera, Zeiss. 4. D. m, of D. magna; 

 c, of D. cuprea. 



Description of Figures, Illustrating Characters of D. Magna. 



Fig. 1. Pointed seta. 



Fig. 2. Hook seta of first parapodium. 



Fig. 3. Side view of anterior region. 



Fig. 4. Dorsal view of posterior end. 



Fig. 5. Chisel-shaped seta. 



Fig. 6. Hook seta of 40th somite. 



Fig. 7. Jaws: A, dorsal jaw pieces; i?, ventral jaw pieces; /and r, left and right 

 dental plates; l\ unpaired left piece; l' 1 , / 3 , / 4 , and r 2 , r' 3 , r*, left and right para- 

 gnaths. 



