FKOM THE EDDYSTONE GROUJJDS TO STAllT POINT. 457 



Plumularia frutescens. A very fine specimen in haul 10 (Ground 

 XVI.), 5-6 inches high, growing on a Pedcn maximitH shell. 



Distribution. Geographical. Britisli Coasts, Algoa Bay (Krauss) [fide Hincks, No. 

 46]; Mediterranean [fide Carus, No. 14). 



Depth. 5-34 fathoms (Schulze, No. 105, Pommerania). 



Habitat. On stones and shells in deep water (Hincks). The Pommerania took the 

 species twice, on shells and stones (34 fathoms) and on stony ground (5-10 fathoms). 



ACTINOZOA. 

 [Nomenclature : — Gosse, No. 30 ; or Had don. No. 35.] 



Alcyonium digitatum. The relative distribution of Alcyonium on 

 the grounds examined is indicated in Chart I. Large colonies are 

 abundant on the fine sand of the outer trawling ground (Ground II.), 

 where they are generally fixed to Carclium cchinatum shells, and also 

 on the fine sand of Ground VI., south of the Eddystone, where they 

 are attached to shells of various kinds. Large colonies are also 

 abundant in the two deepest hauls on the Bolt Head Shell Gravel 

 (hauls 27 and 28), and in the deeper hauls on the Prawle Stony 

 Ground (hauls 4, 45, 66). On the other grounds near the Eddystone, 

 and in the remaining hauls on the Bolt and Prawle Grounds, young 

 colonies are frequently met with growing on living Pecien opercularis or 

 on shells of different kinds, but they seldom, if ever, attain any 

 considerable size. 



It will be seen from the chart that all the grounds indicated above, 

 upon which large colonies are taken, lie at depths of 34 and 35 fms., 

 and are in fact the deepest portions of the area investigated. Other 

 situations in which Alcyonium flourishes in the neighbourhood of 

 Plymouth show that depth in itself can only indirectly influence its 

 distribution, and that the species can also adapt itself to a variety 

 of conditions of density, temperature, etc., without injury. For 

 instance, very fine colonies are often found growing a few feet only 

 below low-water mark, on the iron pillars supporting the Promenade 

 Pier within the Sound. Colonies of moderate size are also found, 

 exposed at low water, on the Eddystone rocks, attached to the over- 

 hanging ledge beneath the remains of the old lighthouse, on the more 

 sheltered side of the rock. 



Two of the most important factors which determine the local dis- 

 tribution of the species would appear to be (1) the presence of suitable 

 objects upon which it can fix, and (2) the absence of movements of the 

 water strong enough to break the colony from its base or to overturn 

 the object to which it is attached. Since the species can fix to rocks, 

 to stones, or to shells, the first of these conditions is fulfilled upon all 

 the grounds examined in the present investigation, for suitable shells 

 at least are everywhere found, so that the second becomes of the more 



