806 MR. J. uiTCiiiE ON iivDHuiDS [May 24, 



as in simple Canniauuhiriiin liydroids, regeneration is not content 

 with siiM[)ly adding a portion to tlio old stalk, bnt a complete new 

 stalk is rt'iirodiiced, springing from within the truncated end ot" 

 the old one. 



Dimensions : — 



Stalk, length ((•43-0-98 mm. 



,, diameter 0-U6-0-08 mm. 



Stolon, diameter O'lO mm. 



Hydranth, length 0-84-0-36 mm. 



„ greatest brea<lth 0-11-0-21 mm. 



Cnidoblast threads, armed with har])s such as Kirkpatriek has 

 figured, accompany several of the hydranths. They are remark- 

 able for their large size, the barbed })ortion being 6 ^ in diameter 

 from tip to tip of the bai'bs. 



Localities. Rare hydranths on Thyroscyplms vitiensis and on 

 Idia pristis from St. 1, east of Tavoy Island and Port Owen, 

 4 to 12 fathoms, sand and broken shells, and mud. A solitary 

 hydranth on Idia pristis and a few on Corydendrium sessile from 

 St. 35, between Warden Island, Howe Island, and Lyall Island, 

 15 to 20 fathoms, rock and sand. 



The species has been previously I'ccorded oidy from j\Turray 

 Island, Torres Straits, 15 to 20 fathoms (Kirkpatriek, 181)0. p. 60(5); 

 and, in Indian seas, from Paumben, 1 to 3 fathoms (Jiiderholm, 

 1903, p. 263). 



Family P e n x A R i D .e. 



*Penxaria disticda Goldfuss, 1820. Var. australis Bale, 1884. 

 {^z=Pennaria cavolinii Ehrenberg, 1832.) 



A few well preserved colonies, the largest 30 uim. high, 

 represent this species. The ramules from which the hydranths 

 project increase considerably in diameter upwards from their 

 origin, where they bear three or four annulations, to the distal 

 end, which is smooth. The number of liliform tentacles varies 

 from nine to twelve, but there is much variation in the number 

 of the capitate tentacles. The numbers depend, to some extent, 

 iipon the age of the hydranth, for the tentacles are fewest in 

 those hydranths which, springing from ramules, lie towards the 

 distal end of a branch — that is, in the youngest hydranths ; for 

 gT'Owth proceeds by the elongation of a branch, new polyps 

 coming into being next to the terminal polyp, which is the oldest 

 and the largest on the branch. 



Pictet's cai-efnl comparative study of colonies of typical 

 1'. cavolinii from Naples, and of ty[)ical P. australis from 

 Amboyna. makes clear that the latter form falls within the 

 range of variation observed in the former species. But so 

 detuiitely limited is the ba.sal ringing of the ramules from 

 which the livdrauths arise, and .so great a difference is there 



* For sy 11(111 viiiy, sec Ik-ilot, lOOl. ii. 459. 



