118 F. W. GAMBLE, M.SC,, AND J. H. ASHWORTH B.SC. 



agree in the chitinous spines tipping the proboscis papillae, the buccal 

 papilla?, the strong retractors of the "proboscis," the capacious and 

 largely unsegmented coelom, the general character of the musculature, 

 the thin-walled looped alimentary canal with its ciliated ventral groove, 

 the action of the body-wall in producing waves of coelomic fluid auxiliary 

 to the process of burrowing and defalcation, and lastly, the pigmented 

 nuchal organ. If we acknowledge the many points of agreement, 

 which have for the most part arisen independently, between these two 

 distantly related families under similar conditions of life, the true 

 relationship between Arenicola and othera genera of Polycheets can 

 only be ascertained by exercising the greatest caution in not confusing 

 convergent adaptational characters with true genetic resemblances. 



Note to Page 110. 

 The vessel printed in red on Plate VII., Fig. 5, and lettered N. Eff. 4 , is in 

 reality a solid cord of connective tissue accompanying the afferent vessel 

 (N. Aff. 4 ) of the fourth nephridium. November 11th, 1899. 



13. LITERATURE. 



1838. Milne-Edwards, A. — " Recherches sur le circulation des Annelides," 

 ' Ann. Sci. Nat.,' ser. 2, t. x, 1838. 



1880. COSMOVICL— ' Arch. Zool. Expt.,' vol. viii., 1879-80. 



1881. Verrill, A. E. — ' Trans. Connecticut Academy,' vol. iv., pt. 2, 1881. 



1882. Krukenberg, C. F. W. — ' Vergleich. Anat. Studien,' Zweite Reihe, 



Zweite Abtheil., Heidelberg, 1882, p. 87. 



1883. WireV. — "Cluetopoder fran Sibiriska," ' Vega-expeditionens Vetensk 



Takttag,' Bd. ii., 1883. 

 1883. Levinsen. — " Systematisk-geograph. Oversigt over de Nordiska Annu- 



lata," « Vidensk. Meddels. Kjobenhavn,' 1882-3. 

 1887. Cunningham. — ' Quart. Journ. Micros. Sci.,' xxviii., 1887-8, p. 239. 

 1887. Marenzeller. — 'Zoologische Jahrbucher,' Abth. f. Systematik, Bd. 



in., 1887, p. 12. 



1887. WlREN.— ' Kongl. Vetenskamps-Akad. Handlinger.' 1886-7. 



1888. Cunningham and Ramage.— ' Trans. Roy. Soc. Edinburgh,' vol. 



xxxiii., 1888. 



1889. MacMunn.—' Quart. Journ. Micros. Sci.,'xxx., 1889-90, p. 74. 

 1891. CuENOT. — 'Arch. Zool. Expt.,' ser. 2, vol. ix., 1891. ' 



1891. Davison.— ' Geol. Magazine,' vol. viii., 1891, p. 489. 



1892. Ehlers.— 'Zeit. f. wiss. Zool.,' vol. liii., Suppl., 1892. 

 1892a. Ehlers.— 'Gottingen Nachrichten,' No. 12, July 27th, 1892. 



1893. Benham.—' Journ. Marine Biol. Assoc.,' N.S., vol. iii., p. 48. 



1894. Schaeppl— ' Jenaische Zeitschr.,' Bd. xxviii., 1894, p. 247. 

 1896. RACOVITZA.— ' Arch. Zool. Expt.,' ser. 3, vol. iv., 1S96. 



1896. Kyle.— ' Annals and Mag. Nat. Hist.,' ser. 6, vol. xviii., 1896. 



