!8 vSTYI.ASTRRIDAE 



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

 aud 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 Hick son's view were correct, that the spermarium of the gouophore is surrounded by a thin eudoderm 

 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 PI. 30 fig. 15) of the yong gono- 

 phore in Dislichopora. 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 Stylaster 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 uorvcgicus. 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 Gunnerus (1768 p. 64), who calls it Mille- 

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

 which Liune described somewhat later in the nth edition of the Systema naturae. The original 

 specimens of Gunnerus 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 

 Eh 1 en berg under the name of Allopora oculina. In Milne-Edwards' diagnosis of the latter 

 species (1857 p. 132) we find: Coenenchyme tres-developpe, couvert 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. Oil 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 uorvcgicus, 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 Ehr en berg's Allopora oculina. G. O. Sars was the first to describe the conditions 

 in a living Stylasterid, after studying colonies of Stylaster norvegicus out on Storeggeu 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 essentiall}- different from the other corals and probably does not belong 

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



') i. e. the investigation. 



