PLATE 5. 



Fig. 1-5. DoL.'iBELL.'V AGASSIZI, Sp. IIOV. 



Fig. 1. Genital ganglion complex; gn, the genital nerve from the visceral ganglion (Plate 3, 

 fig. 2, 2h3), temunating in a group of ganglia at the right margin of the adnexed genital mass 

 (c/. Plate 5, fig. 4, g.g.); a, fine nerves to dorsal peritoneum; h, nerves ramifying to the small 

 hermaphroditic duct; c, nerves to the small hermaphroditic duct and to the ovotestis; d, nerves 

 to the adnexed genital mass. X 50. 



Fig. 2. Ventral view of central nervous system to show the relations of the parapedal com- 

 missure; ao, aorta; s-b.a, subbulbar artery; I. -p. a, left pedal artery; r.p. a, right pedal artery; 

 p-p. c, parapedal commissure, connecting the two pedal gangha, shown above the aorta; a and h, 

 paired nerves arising from the ]3arapedal commissure; d, /, branches to diaphragm; h, branch to 

 peritoneum; c, the unpaired median nerve from the same source; 1-9, pedal nerves in ventral view. 

 X 5. 



Fig. 3. The four innermost lateral teeth of the thirtieth row of the radula seen obliquely from 

 above. The teeth are numbered from within outward. The hook of the fourth tooth is double and 

 the tip of the base of the same is also bifid (cf. Plate 5, fig. 5). X 100. 



Fig. 4. Reproductive system as seen from below, the parts lying in their natural relations; 

 sm. h. d, the small hermaphroditic duct, its free end, oc, arising in the ovotestis, which is not repre- 

 sented, the closely convoluted turns of the duct narrowing on reaching the right posterior angle of 

 the adnexed genital mass, a. g. vi. It passes diagonally forward across the ventral face of the 

 latter, forms a loop upon its dorsal surface and returns ventrally as sm. h. d', to open into the fertiliza- 

 tion-chamber, /. c. ; c. d, copulatory duct opening into the fertilization-chamber and receiving the long 

 duct of Cuvier, d. C, from the spermatocyst, sp. c. Into the fertilization-chamber also open the. con- 

 voluted portion of the nidamental gland dimly seen in the anterior part of the concave face, and the 

 albumen gland, not visible in tliis view; ov-sp. d, the ovospermatic duct, the continuation of the spiral 

 portion of the nidamental gland into the large hermaphroditic duct, I. h. d; r. s, its blind sac-like diverti- 

 culum, the seminal receptacle, near the distal end; .sp. th, the spermatotheca, or vesicle of Swammer- 

 dam, opening by its long slender duct, into the distal end of the large hermaphroditic duct; i, edge of 

 a small flap of integument cut from the body-wall, through wliich the large hermaphroditic duct opens 

 in the common genital orifice; pi. v. con, the left pleuro-visceral connective; pi. par. con, the right 

 pleuro-parietal connective; I. v. g, left visceral ganglion; r. p. g, right parietal ganghon; v. 1, first vis- 

 ceral nerve to spermatotheca; v. 2a, right main branch of second visceral nerve, its branch v. 2a' , to 

 the organ of Bohadsch etc., and v. 2a" forking to rectum and anus; p. 1, first parietal nerve to vulvar 

 region; p. 2, second parietal, or osphradio-ctenidial nerve; v. 2b, left main branch of second visceral 

 nerve, ramifying to the genital gangha, g. g., and to the heart, pericardium, kidney, etc. X 1.5. 



Fig. 5. Four innermost teeth of the fifty sixth row of the radula, corresponding in position to 

 those shown in Fig. 3. The same double characteristics appear in the fourth tooth that were found 

 in the preceding row, shown in Fig. 3, and in all the intervening ones. X 100. 



