r>VOLUTION WITHIX rUK GKN'CS DEXDIlONRPIirnVA. 33 



4, Evolution within the (leniis JJeiHlroni'plithija [Spongodes) 

 (Alcyonaria), with descriptions of a number of species. 

 Bj W. Rae Sherriffs, M.A., D.Sc, F.L.S., Lecturer 

 in Zoology, University College, Southampton*. 



[Received August 10, 1921 : Read November 8, 1921.] 

 (Plates I.-III.t ; Text-figures 1-30.) 



Paet I. — General. 



§ 1. All who have worked at Alcjonarians will agree as to the 

 ditiiculties presented by the genus Dendroneplithya or Spongodes. 

 For here we have to deal with a multitude of species within 

 a relatively narrow range. Thus Kiikenthal, in his ' Versuch 

 einer Revision der Alcyonarien : II. Die Familie der Neph- 

 thyiden, 2. Teil ' 1905, deals with no fewer than eighty-seven 

 species ; and Henderson, in the ' Alcyonarians of the Indian 

 Ocean,' Part II. 1909, with another series of sixty different from 

 the former. And yet in both cases the species are described in 

 minute detail. 



The continual experience in investigating a collection of repre- 

 sentatives of this genus is that, in spite of an initial determi- 

 nation to refrain from adding to the already large number of 

 described species, one is forced to do so. And there is no 

 denying that each of these new forms has a distinct individuality. 

 This experience inevitably raises a number of setiological questions 

 which it may be useful to state,. although they cannot be more 

 than partially answered. Some of them at least could be replied 

 to by an investigator in a good locality, having at his command 

 a large number of specimens of any given form. 



§ 2. The outstanding phenomena which present themselves are, 

 apart from the multitudinous species, the following : — 



A. That the specific distinctions are all of a relatively trivial 

 sort, such as mode of branching, grouping of polyps, length of 

 polyp stalk, strength of supporting bundle, jDresence or absence 

 of a definite " crown," the number and the arrangement of the 

 spicules in the anthocodial points, the distinction between the 

 cortex of the polyparium and that of the "sterile stalk," and the 

 nature of the spiculation of the canal-walls. 



B. That the species difier one from the other to a large extent 

 in the congeries or collocation of such characters as we have 

 mentioned ; that is to say, two species with similar anthocodial 

 armature may dLfter in the mode of branching, and vice versa. 



C. That within the limits of a colony there is, in most cases, 



* Communicated by Prof. J. Aethue Thomson, M.A., LL.D. 

 f For explanation of the Plates see p. 77. 



Proc. ZooL. Soc— 1922, No. III. 3 



