Haddon and Dixon — The Structure of Feachia hastata. 403 



Gosse with sufficient minuteness, we therefore deem it advisable to 

 add a few words on the subject. The anatomical relations of this 

 organ we reserve for our second communication ; suffice it now to 

 state that it is situated at one extremity of the mouth, and that it 

 is manifestly formed by two folds uniting with each other, the line 

 of junction being towards the mouth, and opposite the side we term 

 the base. The free edge of the tube thus formed is prolonged into 

 a number of processes — from six to twenty. The simplest state we 

 have seen is that shown in PI. XYI., fig. 5, where there are six 

 nearly equal lobes — in all other specimens the basal and both ter- 

 minal lateral lobes are larger and more complex than the others. 

 They, and more especially the two latter, may give rise to several 

 secondary processes, till the organ attains a very complicated ap- 

 pearance. It appears to us not improbable that there are but 

 really three primary lobes, and that the varying number of pro- 

 cesses may be but complications of the same. As has been already 

 noted above, there is a dark central core ; a white streak may 

 usually be traced running from one papilla to another, and termi- 

 nating at the apex of each. This organ is very extensile, and 

 admits varied movements both as a whole and in its parts. 



The observation of the physa in living specimens is rendered 

 very difficult by its being almost always more or less introverted. 



When it is fully distended a number of apparent perforations 

 may be seen ranged in linear series along the radii, they do not 

 extend to the scapus; no posterior pore appears to be present 

 during full distension. 



When in a state of partial distension the introverted base 

 appears perforated; but this may be an optical delusion, as may 

 also the above-mentioned thin spots, which are slit-like, or round, 

 according to the amount of distension of the physa. (PL XYIIL, 

 figs. 3 and 4). 



Habits. 



Feachia hastata makes for itself a burrow in the sand eight 

 or nine inches deep. Sometimes it extends itself perpendicularly 

 from this hole to a height of three or four inches, but usually it 

 spreads its tentacles just over the surface of the sand, and it may 

 often be seen with its tentacles withdrawn while the conchula is 

 still protruded level with the top of its hole. When left dry by 



