Report on the Hydroids. 375 



(PI. XXIV, fig 1). When the hydranth retreats from the wall to develop 

 its tentacles, the operculum follows, and at the same time the roof 

 of the hydrotheca crumples up and is thrown off at once or later. 

 On some hydrothecae, in which the tentacles of the hydranth were 

 not yet completed, I have opened the operculum artificially, and in 

 some cases I have seen its rim to be cjuite free, the roof thrown off 

 and the hydrotheca thus quite complete; in other cases the roof 

 remains as a crumpled mass, which is totally thrown otT when the 

 completed hydranth comes out. — The operculum is generally exter- 

 nal, but it may also be internal or lateral. 



Stolon isation (bridges, coalescences and tendrils) occurs here 

 in the same way as in Lafoëa friiticosa (see p. 355 — 356 and PI. XX, fig. 4). 



Gonosome: I have found the hitherto unknown gonosome on 

 two colonies from St. 71 a. It is a typical "Coppinia". The gono- 

 thecae (text-fig. 4.) are 5 — 6 cornered, ca. 125 ^« 

 diagonally ; their free surface is broadly coni- > ^"^"^ ^ 



cal, ca. 25// high; then from the middle rises 1 ^2s^ \ 



a cylindrical neck, 25// high and 25// in dia- ! | — t- i----.v 



meter; on gonothecae which touch one of the ' J — L^- --; — ± 



long, narrow hydrothecae, the mouth is not '<f— 



in the middle but close in towards the hydro- I 



theca (PI. XXIII, fig. 7). These gonothecae are 1 



connected into oblong masses on the branches, \ 



1.5 — 2 mm, in diameter, ca. 10 mm. long (PI. I 



XXIII, figs. 5, 6). The hydrothecae between Text-fig 4 



the gonothecae are long, thin (diameter ca. 90/^), 



and strongly, but regularly curved in such a manner that they form 



a mantle, ca. 0.75 mm. thick, round about the gonothecae and of 



almost the same denseness everywhere. The whole Coppinia thus 



has a diameter of ca. 3 mm. It is of special interest, that the long, 



thin hydrothecae mentioned are provided with an operculum of quite 



the same construction as in the normal hydrothecae (PI. XXIII, fig. 8). 



The wall of the Coppinia hydrothecae is as a rule somewhat thickened 



on the concave side. 



We thus have evidence, that Toichopoma belongs to the family 

 Lafoëidae, in which Broch (17) has also placed it, but only for the 



following reasons, " die einzige bekannte Art zeigt in ihrem Bau 



so unzweifelhafte Beziehungen zu der Gattung Lafoëa, dass sie ihre 

 nächsten Verwandten hier sucht". Broch is further of the opinion, 

 that Toichopoma cannot perhaps remain as a separate genus, but is 

 a species of the genus Lafoëa. I think, however, that the presence of 

 an operculum makes Toichopoma so distinct from the other Lafoëidae, 

 that there is sufficient reason for retaining Levinsen's generic name. 



