316 On the Young Stages of a few Annelids. 



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 observa- 

 tions of Desor* hint at some such widely different transforma- 

 tion for the Nemerteans, but his observations are too inaccurate 

 to afford any data for a satisfactory analysis. 



The persistence of the antennas 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 

 Phoronis of Wright, f but with which, from the descriptions given 

 by Allman in his Fresh-water Polyzoa,;}: and by Van Beneden,§ 

 it has not the slightest relationship. On examining subsequent 

 stages this stumbling block 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 Girardf and some of the species of Polia figured by Quatre- 

 fages^ in the Yoyage en Sicile, although as yet I have not been 

 able to trace in the embryo worm anything of the complicated 

 structure of the Nemerteans. 



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

 quarter of an inch; the subsequent changes are principally 

 limited to alterations in the shape of the head, and the gradual 

 disappearance of the articulations, the only trace of them left 

 being the corresponding convolutions of the digestive cavity. 



* Desor E. ; On the Embryology of Nemertes. . . .in Proc. Bost. Soc. Nat. Hist. 

 Vol. VI., p. 1, 1848. 



f Wright T. S. ; in Edinb. New Phil. Journ., 1857, V. 



\ Allman J. G. ; A Monograph of Fresh-water Polyzoa, p. 55, note. 



§ Van Beneden P. J.; Note sur un Annelide Cephalobranche sans soies, designs 

 sous le nom de Crepina; in Bull. Acad. Roy. de Belgique, 2de Ser. V., No. 12. 



|| Girard C. ; in Smiths. Cont. q. a., 1853. 



\ Quatrefages A. de ; Memoire sur la famille des Nemertiens; in Recherches 

 Anatomiques. . .voyage sur les cotes de la Sicile. .. .Vol. II., par H.Milne 

 Edwards, A. de Quatrefages et E. Blanchard. 



