Hydroida fi-om Deej) Water. 135 



species, so that Lafoeina tenuis must take its place in our 

 fauna. At the time I noticed tlie transparent clavate processes 

 associated with the calycles, but supposed them to be some 

 parasitic growth. 



A question may arise wliether Guspidella humilis is a 

 distinct form at all, or whether it has been founded on ex- 

 amples of Lafoeina. I have been able to settle this point 

 conclusively by a reference to specimens of the former ; and 

 Sars, who is intimately acquainted with the latter Hydroid, 

 includes Cusjndella humilis also in his list of Norwegian 

 species, and therefore recognizes them as distinct. 



I have carefully re-examined the other species of Guspi- 

 della (C. grandis and C. costata), and find them to be un- 

 doubtedly destitute of the appendages. 



Gonothyrcea hyalina^ Hincks. 



This fine species I have referred provisionally to Gono- 

 thyrcea''', having only had the opportunity of examining im- 

 mature gonophores on specimens preserved in spirit. Sars, 

 however, has obtained it at Lofoten with fully developed 

 gonophores exhibiting the characteristic structure of this 

 genus, and has thus definitely settled its systematic position. 



Acaulis primariuSj Stimpson. 



We have hitherto known this interesting Hydroid im- 

 perfectly, through the description of it given by Stimpson in 

 his ' Marine Invertebrata of Grand Manan.' 8ars, however, 

 has obtained it in deep water (40-100 fathoms) off" the Norwe- 

 gian coast on muddy ground, and has thoroughly investigated 

 its structure. 



The two most important points which he has determined are 

 the mode of its attachment and the history of its reproduction. 

 Stimpson found his specimen floating in the open sea, and 

 describes Acaulis as permanently free. It appears, however (as 

 Allman had conjectured) that this is an eiTor ; the stalk-like por- 

 tion of the body below the aboral wreath of tentacles is invested 

 by an exceedingly thin hyaline skin, wliicli passes far beyond 

 its free conical extremity in the form of a perfectly trans})arent 

 slieath, and towards the base is thickly covered with small 

 grains of sand and fragments of mud. By means of this 

 sheath the polypite no doubt roots itself in the sand or ooze, as 

 Corymorpha seems to do by the help of a very similar 

 structure. The reproductive bodies are sim])le fixed sporosacs, 

 developed in great number immediately above the proximal 



• Hislorj' of IJrit. Hydr. Zooph. i. 184, pi. xxxv. figs. 2, 2rt. 



