AREHTCOLA ECAUDATA. 77 



pairs of gills are present, but the caudal region with bristles is longer. Except the 

 simple gill on the fifteenth, all show short secondary processes, especially anteriorly 

 where they form short branched tufts. Moreover, another example almost the same 

 length had somewhat longer gills in front, whilst a third agreed with the first. 



The fourth stage is 16 mm. long, from Salthill, Co. Dublin, in August. The pigment 

 is boldly marked anteriorly, the snout in front of the nuchal groove being dark brownish 

 (in spirit), the nuchal grooves forming a broad V with the concavity forward. Then a 

 broad dark belt succeeds with a paler area behind. This is followed by three blackish- 

 brown segments, and the rest of the body is pale brown. The bristle-tufts and the rows 

 of hooks are marked by pale areas and bands, the latter continuing after the branchiae on 

 the sixteenth make their appearance. The gills are longer and more distinctly branched. 



When If in. long it is found, amongst other situations, at Lochmaddy in the interstices 

 of the roots of Lainhiarise dredged beyond low- water mark. The colour is dull greenish- 

 yellow with very finely-branched red branchiae, though the tips of these organs are paler, 

 apparently from the minute subdivision of the branches. Branchiae were not observed on 

 the four segments in front of the pygidium. Anteriorly the segments are distinctly marked 

 —broader in front, narrower posteriorly. The snout is slightly redder than the rest of 

 the body. 



Gamble and Ash worth (1900) state that the post-larval form may be distinguished 

 from that of A. branchialis, which also has statocysts, and the gills and feet are continued 

 to the posterior end of the body, by the presence of thirteen pairs of segmental organs. 



Habits. — It frequents tracks under littoral stones and in clefts of rocks, and has no 

 regular burrow as in A. marina. At Valencia a little sand and fragments of Fucus occur 

 in the gut, and the coarse fcecal coils do not form piles as in A. marina, some falling to 

 pieces, in this respect agreeing with A. branchialis (Gamble and Ashworth). It secretes 

 abundant and tenacious yellowish-green mucus as in A. marina. Fauvel found that at 

 night captive specimens left the sand and moved about at the surface of the water, 

 swimming freely. 



Naturalists owe this species to the acuteness and life-long devotion of Dr. George 

 Johnston, of Berwick, who recognised its distinction from the common form. He 

 mentions that the smallest number of pairs of branchiae he had met with was twenty- 

 two, and the first few pairs were smaller than those about the middle, whence they 

 again decreased towards the tail. He separated the variety branchialis as a distinct 

 species, and mentions three varieties of Leach's in the British Museum, viz. nodosa, 

 Montagni, and Dorvilliana. 



This lob-worm formed the subject of the first chapter of Grube's ' Anatomie u. 

 Physiologie der Kiemenwurmer ' in 1838, and his treatment of it, structurally and other- 

 wise, was in consonance with the distinction he afterwards achieved in the department.- 



A figure (Plate XXIX, fig. 33) given in Delle Chiaje's 'Memorie' (1828), though 

 inexact, may refer to this species, since the branchiae are carried to the tip of the tail. 



The A. Montagui of Leach in the British Museum is this species. 



Rathke 1 (1843) considered this form different from A. branchialis of Milne Edwards, 

 and apparently it was a young example, measuring 1^ in. in length, 



1 ' Fauna Norwegens/ olim cit. 



