Description of Plates 173 



PLATE IX. 



Fig. 19. A. ecaudata Johnston, from Plymouth (August, 1910). Dissection of 

 the anterior portion of a mature male example. The specimen was 

 opened along the mid-dorsal line. The portion of the oesophagus 

 between the glands and the hearts is unusually extended and dilated 

 with food. The testis on the fifth left nephridium is produced into 

 two thin outgrowths, one overlying the other, and the testis borne 

 by the third right nephridium presents a similar condition ; each of 

 the other testes bears only one such outgrowth (see PL XV. Fig. 53). 



Fig. 20. A. branchialis Audouin and Edwards (A. grubii Claparede), from 

 Plymouth. Dissection of the anterior portion of a mature specimen ; 

 the reproductive organs are small (see PI. XV, Fig. 51). 



PLATE X. 

 Figs. 21-25. A. p usilla Quatrefages (A. claparedii Levinsen). 



Fig. 21. Larva, about thirty hours after fertilisation of the egg ; ventral aspect 

 (see p. 74). 



Fig. 22. Larva, dorsal aspect ; about forty hours older than the preceding, 

 and on the point of forcing its way out of the vitelline membrane, 

 through the thin area in the upper part of the same. 



Fig. 23. Larva, one day after hatching ; dorsal aspect. The larva was 

 slightly compressed under the cover-glass, and therefore appears a 

 little too broad. The first notopodial chaetae have been formed. 



Fig. 24. Larva, twelve days after hatching ; right aspect. The middle portion 

 of the gut still contains yolk. Note the two kinds of notopodial 

 chaetae and the crotchets. 



Fig. 21-24 were drawn, in Naples, from living larvae, which had 

 developed from eggs fertilised artificially. 



Fig. 25. One of the eyes of the larva shown in the preceding figure. Note the 

 cup-shaped group of pigment-spherules, and the lens (see p. 70). 



Figs. 26-28. A. marina (Linnaeus), from Plymouth (see p. 77). 



Fig. 26. Post-larval example, 4' 7 mm. long, in its mucous tube, as found in 

 the plankton. 



Fig. 27. Post-larval example, about 6 mm. long; anterior end, dorsal aspect. 



Fig. 28. Left aspect of the anterior portion of a stained and cleared post-larval 

 specimen, 4 5 mm. long. 



Fig. 29. A. assimilis Ehlers var. affinis Ashworth. Left aspect of the anterior 

 portion of a stained and cleared post-larval specimen, 11 mm. long, 

 from the Falkland Islands (see p. 80). 



Fig. 30. A. cristata Stimpson. Post-larval specimen, 6 mm. long, from 

 Wood's Holl, Mass., showing the full number of tail-segments and 

 the incipient gills (see p. 79). The neuropodial crotchets are 

 indicated by vertical series of white dots. 



