156 SIDNEY F. HARMEtl. 



fig. 9. la the individual referred to, the stalk portion of the 

 vestibule is still present, but is small, and is connected with 

 the oesophagus very much as in the diagram fig. 16 ; i. e. at 

 some distance from the point where the apex of the epistome 

 ultimately meets the vestibular wall. 



In somewhat later stages the permanent mouth is formed by 

 the perforation of the septum between the two portions of the 

 vestibule in fig. 10, and probably in the position of the aper- 

 ture a. V. V. in fig. 16. 



In living individuals of the same age could usually be dis- 

 covered a small projection of the surface of the body in the 

 region marked ? s. in fig. 10. This represents the larval 

 " sucker," which, as Barrois has correctly stated, disappears 

 during the metamorphosis. The region of the "dorsal organ" 

 or brain of the larva is doubtless indicated by the marked angle 

 on the left side of the stalk of the individual just referred to. 

 None of the previous histological peculiarities of the organ re- 

 main at this stage, and it is in fact already almost impossible to 

 distinguish with certainty its position. 



It appears to me that Barrois has suggested the real expla- 

 nation of the metamorphosis of Pedicellina, although he has 

 confined himself to one or two short statements, which are 

 given without any indication of the manner in which they are 

 to be interpreted. I quote below one or two passages from 

 Barrois' note so many times referred to (3), the given quota- 

 tions reproducing, so far as I am aware, the whole of Barrois' 

 explanation of this complicated subject. 



(i) "La premiere position" [corresponding, from the de- 

 scription, with my own fig. 10] " repr^sente un etat tout k 

 fait analogue au Loxosoma, avec anus en haut et oesophage 

 en has." 



(ii) " L'inferieure" [portion du vestibule] ''qui porte la 

 couronne, et dont les elements viennent former la glande du 

 pied." 



(iii) "Les deux organes enigmatiques de I'exoderme" [i.e. 

 sucker and dorsal organ] . . . . " ne sont, suivant moi, que 

 des organes provisoires ; tous deux sont rejetes sur la face 



