58 Prof. Allman on the Hydroida. 



almost exclusively on the hydrocaulus, only an occasional one 

 being here and there developed from the hydrorhiza, while in 

 P.palliatus they are confined to the hydrorhiza, — and in the form 

 of the medusa, whose contracted codonostome gives to the um- 

 brella, at the time of liberation, an oviform shape which is very 

 striking and peculiar, while in P.palliatus the umbrella does not 

 become contracted towards the codonostome, and is accordingly 

 nearly cylindrical in form *. 



In medusse now about the tenth day since their liberation, 

 and still alive in my tanks, the form has undergone considerable 

 change, the umbrella having become nearly spherical, thus pre- 

 senting a further departure from the medusa described by Dr. 

 Wright as proceeding from P, palliatus. No increase, however, 

 has taken place in the number of marginal tentacles. 



Bougainvillia fruticosa, Allman, n. s. 



Trophosome. — Hydrocaulus rising to the height of about two 

 inches, much branched, with the main stems composed of aggre- 

 gated tubes, branches subalternate, periderm of the smaller 

 branches marked by shallow transverse corrugations, which 

 become obsolete on the larger branches and main stems : poly- 

 pites in extreme extension nearly cylindrical, with the periderm 

 continued for a short distance over the posterior part of their 

 body as a thin pellicle, which in extreme contraction appears as 

 a membranous corrugated cup, into which the polypite has 

 become withdrawn for about its posterior third. 



Gonosome. — Gonophores pyriform on distinct peduncles spring- 

 ing from the upper side of the ultimate ramuli, along which they 

 extend nearly from the origin to the termination of the ramulus. 



I met with B. fruticosa in September, growing in abundance 

 on a large piece of floating timber in the mouth of the Kenmare 

 River, coast of Kerry. 



Bougainvillia fruticosa, though closely allied to B. ramosa, Van 

 Ben., differs from it in the more cylindrical and slender form of 

 the extended polypite, in the less extent to which the polypite is 

 invested by the membranous dilatation of the chitinous periderm, 

 and in the disposition of the gonophores. While in B. fruticosa 

 the polypites in extreme retraction have the tentacles and nearly 

 two-thirds of the body exposed, the contracted polypites of B. 

 ramosa are almost entirely concealed within the dilated periderm. 

 In B. ramosa, moreover, the gonophores, instead of being borne 

 along the whole of the upper surface of the ultimate ramuli, are 

 confined to their distal extremity, where they occur singly or 

 in a pair consisting of two opposite gonophores, or else in an 



* See Dr. Wright's description of Atractylis pallida, in Ann. Nat. Hist, 

 for Aug. 1861, p. 129, pi. 4. figs. %&i7. 



