of a few Annelids, 213 



withstanding the different development of Nemerteans observed 

 by MUller*, Buschf, GegenbaurJ, Krohn§, WagencrU, Leuck- 

 art and Pagenstecher^, and others, which, when we know 

 more of the general plan of development of Annelids, may after 

 all not present any greater differences, when compared with the 

 present type of growth, than we find in the embryology of 

 Echinoderms, between the plutean and sedentary mode of deve- 

 lopment. There can be no doubt that we have in Annelids as 

 in Echinoderms closely allied genera undergoing a widely dif- 

 ferent metamorphosis — an additional analogy between these two 

 classes, but not, it seems to me, a sufficient reason for uniting 

 Echinoderms with worms, as has been urged with so much 

 ingenuity by Huxley. The observations of Desor"^"^ hint at 

 some such widely different transformations for the Nemerteans ; 

 but his observations are too inaccurate to afford any data for a 

 satisfactory analysis. 



The persistence of the antenn?e and absence of feet and 

 bristles would show that it belonged to some genus of Annelids 

 as yet not described, the only Annelid, without setae being Pho* 

 ronis of Wright ft, to which, however, from the descriptions given 

 by Allman in his Freshwater PolyzoaJJ, and by VanBeneden§§, 

 it has not the slightest relationship. On examining subsequent 

 stages this stumblingblock is found gradually to vanish by a 

 sort of retrograde development ; and as the little worm grows 

 older it loses little by little the embarrassing appendages, and 

 shows, in the most advanced stages thus far observed, a tolerably 

 close resemblance to such well-known Nemerteans as the Nareda 

 of Girard|||| and some of the species of Polia figured by Quatre- 

 fagesllf in the * Voyage en Sicile,' although as yet I have not 

 been able to trace in the embrj^o worm anything of the compli- 

 cated structure of the Nemerteans. 



The little worm (fig. 11) has now attained a length of one 



* L. c, in Archiv f. Anat. u. Phys. 1847. 



t Entwickelung u. s. w. /. c. p. 107. 



i L. c, in Zeitsch. f. wiss. Zool. 1853, v. p. 346. 



§ L. c, in Archiv f. Anat. u. Phys. 1856, p. 78. 



II Archiv f. Anat. u. Phys. 1857, p. 204. 



II Archiv f. Anat. u. Phys. 1858, p. 569. 



•* ** On the Embryology oiNemertes. ..." in Proc. Bost. Soc. Nat. Hist. 

 vol. vi. p. 1, 1848. 



tt Edinb. New Phil. Journ. 1857, v. 



XX ^ Monograph of Freshwater Polyzoa, p. 55, note. 



§§ " Note sur un Anneiide Cephalobranche sans soies, design^ sous le 

 nom de Crepina,*' in Bull. Acad. Roy. de Belgique, s^*. 2. v. no. 12. 



nil C. Girard, in Smiths. Cont. 1853. 



ill! "Mcmoire sur la faraille des Nemertiens," in Recherches Anato- 

 miques. . . . voyage sur Ics cotes de la Sicile. , , , vol. ii., par H. Milne- 

 Edwards, A. de Quatrefages et E. Blanchard. 



