Vol. IV, part h ixiiiied May 81s/, 1919. 



BIMERIA RIGIDA SI'. N. 



On the Anatomy of a New South Afrio^ p^r^-v. 

 Hydroid, Bimeria rigida sp. n. :^v^^^„^14^x\ 



By 

 Ernest Warren, l>.Nc.(Lond.)> 



With Plates I and II, and 2 text-figures. 



The singular hydroid forming the subject of this paper 

 possesses tentacles which have a somewhat limited power of 

 movement owing to the presence of stiff perisarc which runs 

 along their under surfaces. The specific name rigida has 

 been applied to the hydroid on account of this peculiarity, 

 which, however, is shared, but in a less developed degree, by 

 other species of the genus, such for example as Bimeria 

 vestita Wright. 



The hydroid was found sparingly in the rock-pools at the 

 Three Sisters Rocks, l^ort St. John, Pondoland, in January, 

 1911. The material was fixed in hot corrosive sublimate 

 solution with 1"5 per cent acetic acid, and the sections were 

 stained with Delafield haematoxylin followed by Orange. 



The hydroid is small and clings to sea-weed. The hydi'anth, 

 together with the pedicel, extends about 2-3 mm. beyond the 

 weed. It is of a pale horn-colour and translucent, save for 

 the debris and diatoms which may adhere thickly to the 

 perisarc of the tentacles and body. 



TROPHOSOM^]. Hydrorhiza. — The hydrorhiza creeps on 

 the surface of delicate sea-weeds and sometimes tends to grow 

 vertically upwards in a spiral course around narrow, upright 

 shoots of the Aveed. In addition to this tendency to grow 

 spirally, the hydrorhiza gives off short horizontal outgrowths 



VOL. 4, PART 1. 1 



