840 MR JAMES RITCHIE ON 



In a specimen from Ostend, a stalk has been truncated evidently some distance from 

 the summit, for the chitinous wall is well developed at the point of injury. This specimen 

 has regenerated the top fleshy part of an internode, and, surmounting it, a calyx. The 

 power of regeneration, therefore, is not confined to certain definite cells at the base 

 of the calyx, or at the top of the stalk, but exists at other parts of the stem, and 

 is presumably latent in the cells of any part of it. 



III. Remarks on Related Species. 



The structures which have been described place the Hull specimens within the genus 

 Barentsia ; for I shall endeavour to show that the genera Arthropodaria and Gony- 

 podaria of Ehlers, within one of which they would have fallen, ought not to be retained. 

 The relationships of four European forms belonging to this genus are here considered : 

 Arthropodaria benedeni (Foettinger), Ehlers ; Gonypodaria nodosa (Lomas), Ehlers ; 

 Pedicellina gracilis, Sars ; and Pedicellina belgica, van Beneden. 



(a) TJie Identity of Pedicellina gracilis, Pedicellina belgica, 

 Gonypodaria nodosa ( = Barentsia gracilis). 



As the original description of Pedicellina gracilis by Sars is not available to the 

 majority of students, I give here a translation of the passage : — 



" The stalks of this species are quite smooth, without spines, and are more slender 

 and longer in proportion than those of the foregoing species \_Pedicellina echinata] ; the 

 whole animal is on the contrary less, about 1 line long, and the stalks are of the thick- 

 ness of the finest hair. The clubs [calyces] are less oblong than in the foregoing, and 

 their extremity is occupied by about twenty uniform tentacles. The stalks are a little 

 more slender below than above, but widen close to the proximal end into a short and 

 thick cylinder. The stalks are on the whole of firm consistence, except towards the 

 clubs and the proximal thick part, where they are more soft. They seem, therefore, to 

 bend only at these two places. Upon irritation, therefore, either the uppermost part of 

 the stalk bends, together with the club, whereat the animal acquires a nodding appear- 

 ance ; or the whole, stalk bends upon its base, to the side or downwards. This species 

 was found upon a conglomerate of Serpula, many gathered in a colony as in the previous 

 species. Doubtless this has also similar creeping roots ; but I had not the good fortune 

 to get any of them disengaged, and they cannot be seen rightly under a magnifying 

 glass, owing to the small size of the animal. However, a little process sometimes 

 accompanies the proximal end of the stalk, and this is probably a piece of root." * 



Two figures accompany Sars' description (pi. i. figs. 2a, 2b). In 2a, the natural 

 size of a small colony of three individuals is shown, the stalks being between 1 and 2 mm. 

 long. The other figure is a magnified representation of a single individual. It seems 

 to me that it represents, not the single-jointed form which has been taken as the type of 



* SABS, M., Beskrivelser oy Iagaitagelser over nogle maerkelige eller nye i Habet ved den Bergenske Kyst lebende Dyr, 

 Bergen, 1835, p. 6. 



