268 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the dish, surrounded by a film, of mucus. Although the 

 mouth was opeu it was found impossible to induce the 

 larvae to feed and they died as soon as the yolk in the 

 stomach was absorbed, i.e., about a fortnight after 

 hatching, without having advanced beyond a stage 

 showing three or four chastigerous segments (fig. 77). 



Post-Larval Stages. 



Post-larval stages of A. marina are found in the 

 surface waters of the sea, and are almost invariably 

 enclosed in a mucous or gelatinous tube, which overhangs 

 the worm at each end. The external diameter of the tube 

 is from two to three times that of the animal. The young 

 worm is capable of wriggling movements, which are not 

 seriously impeded by the enveloping tube. 



The term " post-larval stage " was given by Benham 

 to a stage in the development in which the animal 

 possesses the full adult number of segments, and is 

 divisible into an anterior chtetigerous region and a 

 posterior achpetous region, or tail, but in which the gills 

 are not yet completely formed, or have not even made their 

 appearance. By this definition all the pelagic specimens 

 of A. marina which I have examined, with one possible 

 exception, are post-larval stages. This one, a Lytham 

 specimen, 3*9 mm. long, bears the full complement 

 (thirteen pairs) of gills, and all of them except the first 

 two have become branched, being formed of two or three 

 finger-shaped filaments (fig. 56). In this specimen 

 also the annulation is well marked, and the prostomium 

 proportionately smaller than in any of the other specimens 

 examined. This animal has reached the end of the post- 

 larval stage, and would doubtless soon have settled down 

 to its littoral habitat. It is the only recorded specimen 



