EXPLANATION OF PLATE XXIV. 



Fig. 1. — Prostomium and sis metameres between the mid-dorsal and mid- 

 ventral lines. The chaetae are represented in the median 

 line in the median zone. The nephropores are seen near the 

 septal furrow. The size of the black dots represents the 

 size of the sense organs only approximately. 



Fig. 2. — A metamere from the clitellum. Near the mid-ventral line is 

 the oviclueal pore. 



Fig. 3.— The next to last and the last metameres of the body, showing 

 the reversed antero-posterior distribution. 



Fig. 4. — Sense organ cut in longitudnal section, cut., cuticle; gl. c, 

 gland cell; b. in., basement membrane; cir. in., circular 

 muscle; b. c, basal cell; s. e.j sense cell showing one of a 

 group of sense cells and the tapering basal ends; bd. c, 

 supporting cell next to the sense organs; ipi. <•., epidermal 

 cell ; s. h., sense hair protruding through the thinned cuticle. 



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