Explanation of the Plates. 115 



opens. 14a. End view of the foot, showing the arrangement of the three papillae. 

 (Figs. 11 and 14 were drawn from the same specimen.) 



Plate XI. 



Fig. 15. Sketch of the male sexual organs, accessory glands, and posterior 

 crural glands of O. cinctipes (from a dissected, freshly drowned specimen from 

 Richmond, enlarged about twely,e times), ix-xvi, ninth to sixteenth segments, 

 showing the bases of the legs (leg), and in the 9th to 13th the internal parts of 

 the crural glands (c?') also, nv, the two nerve cords, showing scarcely any 

 segmental thickenings, te, testis, s.v, seminal vesicle, v.d, paired portion of 

 vas deferens. V. D, unpaired portion of vas deferens, forming a loop (cut in 

 section in fig. 28). d. ej, ductus ejaculatorius. r. ac. g^, right anterior accessory 

 gland, r. ac. g-, efferent duct of right posterior accessory gland ; r. v, carrot- 

 shaped vesicle of this gland ; r. c, central portion of the gland, round which the 

 end of the anterior accessory gland is coiled ; ap, terminal appendage of the 

 posterior gland. 



Fig. 16. Middle portion of a posterior accessory gland of the same specimen, 

 enlarged sixty times to show the course of the anteHor gland (ac. g'-) over its 

 surface ; the latter gland is shaded where visible, but indicated by dotted lines 

 where hidden from view, and ends blindly at x. v, vesicle, and a^), terminal 

 appendage of posterior gland. 



Fig. 17. Ovary, receptacula seminis (r. s), and the ovarial ends of the oviducts 

 of O. cinctipes (from a freshly drowned ? from Richmond), showing the ova {ov) 

 in follicles, in, thick wall of infundibular part of oviduct, od, thinner wall of 

 the oviduct, per, outer coat of oviduct (peritoneum and muscles). 



Fig. 18. Two embryos from the dissected type specimen of P. sedgwicki, 

 Pure. ; a, large embryo nearest the external opening ; b, the smallest embryo of 

 the same brood. 



Fig. 19. Two embryos from the dissected type specimen of O. cinctipes; a, 

 large embryo nearest the external opening ; b, the smallest embryo of the series. 



Fig. 20. Female genital organs of O. cinctipes (from a freshly drowned dis- 

 sected specimen from Richmond), ov, ovary, r. s, receptaeulum seminis. g, 

 external genital opening, od, oviduct. 



Plate XII. 



Fig. 21. Section through the external opening of the crural gland in the 11th 

 right leg of a cf O. cinctipes (alcoholic specimen from Dunbrody, cut transversely 

 to body ; Zeiss, ^'.j Immers. Oc. ii.). cr, part of the duct of the crural gland; 

 nearer the opening the lumen is cut. p, large papilla, bearing the opening of 

 the crural gland and withdrawn into a cavity, the wall (»'./) of which forms the 

 ring-fold when the papilla is f)rotruded. ex, portion of the coxal organ, passing 

 over at x into the echinate ectoderm of the ring-fold. b. c, blood corpuscles. 



Fig. 22. Section through an expanded coxal organ of O. ciiictipes (9th left leg 

 of a spirit specimen, a ? from Dunbrody, cut transversely to axis of leg, Zeiss, 

 -^^T Immers. Oc. ii.). x, x, boundary between smooth and echinate cuticula. b. c, 

 blood corpuscles, ex, striated epithelium of coxal organ. 



Fig. 23. Section through an invaginated coxal organ of the same specimen 

 (8th right leg cut transversely to the axis of the leg), ex. o, slit-like external 

 opening of the cavity formed by the invagination of the coxal organ, which is 

 represented by the epithelium with smooth cuticula (ex). ■ 



Fig. 24. Diagram showing approximately the arrangement of the accessory 

 glands in the specimen of which fig. 25 is a section through the region indicated ; 



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