ANATOMY OF ABENICOLA ASSIMILIS. 783 



situated (probably) in the first tail segment. The nerve-cord is magnified 

 about 10 times and the cells 40 times. 



Fig. 13. — Shows the size of the otocyst of a specimen (120 mm. long) of 

 A. as si mil is from Uschuaia. The oval outline is a camera drawing of the 

 cuticle which lines the otocyst. The tube which leads from the exterior 

 enters the otocyst near tiie point marked E. T. The otoliths are rounded, and 

 many of them show concentric markings, indicating their deposition in layers. 

 In the centre of several of them small foreign bodies may be distinguished. 

 Attached to some of the otoliths are other small rounded bodies of a similar 

 nature, but which stain more deeply. Tiie minute deeply staining spherules 

 (indicated by the dots) are also composed of a similar substance, x 210. 

 (Cf. Figs. It, 15.) 



Fig. 14. — Camera drawing of the cuticle lining the otocyst of a specimen 

 (128 mm. long) of A. assimilis, var. affinis, from the Falkland Islands. The 

 otocyst is somewhat larger tlian the one shown in Fig. 13. The otoliths are 

 nearly spherical. (They are not all present in one section ; some are added 

 from another section.) The two larger ones are probably the first otoliths of 

 the post-larva, which are easily distinguished by their size from those which 

 are formed later. In the centre of each of the large otoliths an irregular 

 foreign body may be seen, x 210. (Cf. Figs. 13, 15.) 



Fig. 15. — Camera drawing of the cuticle lining the otocyst of a specimen 

 (136 mm. long) of A. assimilis, var. affinis, from Otago Harbour. The 

 otocyst is much smaller than either of the two preceding. Tiie otoliths are 

 irregular bodies, chiefly quartz-grains, but two small fragments of spicules 

 {Sp.) are seen lying close together, x 210. (Cf, Figs. 13, 14.) 



Fig. 16. — Camera drawing of the cuticle lining the otocyst of A. marina 

 (about 10 inches long). The tube connecting this otocyst to the exterior is 

 almost blocked, and in consequence the otoliths, which were originally small 

 irregular foreign particles, are now assuming a rounded outline, due to the 

 deposition upon them of layer upon layer of secreted substance; see, for 

 example, the otolith containing the spicule fragment [Sp.). Note the small 

 size of the otocyst compared to those shown in Figs. 13, 14, and 15. x 210. 



Fig. 17. — Fifth nephridium of A. assimilis (specimen from Punta 

 Arenas). The dorsal lip of the nephrostome {Nphm.D.) bears the usual 

 ciliated vascular processes, while the edge of the ventral lip {Nphm. V.) is 

 thrown into numerous folds or frills. Note the gonad, a somewhat club- 

 shaped mass of cells around the gonidial vessel (seen by transparency through 

 the gonad), x 10. 



Fig. 18. — Left aspect of the anterior portion of a post-Inrval specimen of 

 A. assimilis, var. affinis, from the Falkland Islands. The total length of 

 this specimen is ITl mm. Note the four cup-shaped eyes on the prostomium. 

 Between the prostomium and the first cha;tigerous segment is a region 



