18 STYLASTERIDAE 



fibrillar protoplasmic structure of the inner cells is still more marked at this late stage than before 

 and is most distinctly seen in the distal part of the developing organ. - - I did not succeed in finding 

 a fully formed seminal duct. 



We have now the question: from which cell layer arise the inner cells of the duct, are they 

 ectodermal or endodermal? The question cannot be answered on the basis of the present investigations 

 If Hickson's view were correct, that the spermarium of the gonophore is surrounded by a thin endoderm 

 layer, their origin from the endoderm would be a consequence. But the investigations give no support 

 to this view and it is contradicted by Hickson's own figure (1891 PL 30 fig. 15) of the yong gono- 

 phore in Disiichopora. The endodermal layer round the spermarium might be a later formation, but 

 this theory does not find any support either in the present investigation. Provisionally therefore the 

 question of the origin of the inner cells in the seminal duct must remain unanswered. 



The female gonophores agree down to the smallest detail with those of Styla-ster gemmascens. 

 The mature egg is surrounded by an ectodermal layer and in Stylaster norvegicus no indication can 

 be found either of an endodermal layer between the egg-cell and the ectoderm, as Hickson (1891 

 p. 390) has found to be the case in Distichopora. During the development of the egg the spadix 

 atrophies and the pictures obtained of the condition in Stylaster gemmascens (PI. V figs. 46. 29 and 50) 

 are fully illustrative of the conditions in Stylaster norvegicus. Here also I did not succeed in finding 

 the young developmental stages of the female gonophore. 



The first description of the species is found in a paper of G u n n er u s (1768 p. 64), who calls it Mille- 

 pora norvegica. In an appendix (1. c. p. 67) he states that the species is identical with Millepora aspera 

 which L,inne described somewhat later in the nth edition of the Systema naturae. The original 

 specimens of G tinner us are preserved in the Zoological Museum of Trondhjem; one of them is 

 represented in fig. 12 PI. II. - - It is doubtful if it really is the same species which is described by 

 Ehrenberg under the name of Allopora oculina. In Milne-Edwards' diagnosis of the latter 

 species (1857 p. 132) we find: Coenenchyme tres-developpe, convert de points tres-serres, visible seulement 

 avec des verres grossissants. This does not agree with the quite smooth surface, which is characteristic 

 of Stylaster (Allopora] norvegicus. On the other hand, the specimens which are sometimes referred to 

 in the literature from the Norwegian west coast under the name of Allopora oculina are undoubtedly 

 identical with Stylaster norvegicus, the only Allopora met with in the northern Atlantic. It is this 

 species which formed the basis of G. O. Sars' classical investigations (1873 P- 45)> in which he restores 

 the specific name of Gunnerus but refers it to the genus Allopora; he is of opinion that the species 

 is identical with Ehrenberg's Allopora ocidina. G. O. Sars was the first to describe the conditions 

 in a living Stylasterid, after studying colonies of Stylaster norvegicus out on Storeggen on the west 

 coast of Norway. He was in doubt as to the coralline nature of the animal, as he never succeeded 

 in observing the extended polyps, when the colonies were at rest in sea-water, as is the case in our 

 northern corals otherwise, and when he later studied the preserved animal somewhat more closely he ex- 

 pressed his opinion (1. c. p. 46): though I am far from considering this ') as completed, yet I have already 

 learnt this much, that the animal is essentially different from the other corals and probably does not belong 

 at all to the Anthozoa but rather to the Hydrozoai., As is well-known, Moseley a year later (1878) 



') i. e. the investigation. 



