Notes on the Didemnidae (Ascidiacea). III. A Comparison ofDidemnum maculosum, D. candidum, D. helgolandicum, andTrididemnum alleni

Abstract

When Michaelsen (1923) described a species of didemnid from Heligoland, he stated that it was very similar toLeptoclinum maculosumMilne Edwards (1841), so far as may be judged by external appearance, but since no adequate description of this latter existed he proposed to call his Heligoland form by a new name,Didemnum helgolandicum, rather than use an old name which might well be wrong. Neither Michaelsen nor Hartmeyer, who described further details ofD. helgolandicum(1924), was able to compare it directly with specimens ofD. maculosumfrom the Channel coasts whence it was first described by Milne Edwards. Through the kindness of the directors of the Zoological Museum of Copenhagen and of the Biological Station of Roscoff I have been able to obtain specimens of both these forms and to compare them with specimens collected around Plymouth and on the coast of North Wales, and with specimens ofD. candidumSavigny, collected at Naples, and from the Red Sea, and ofTrididemnum alleniBerrill, collected around Plymouth.

The Ascidians of the Japan Sea. I

“…The larvae of T. alleni have only 2 attachment processes, but unfortunately Romanov failed to find any larvae in his specimens. Further, T. alleni has only been recorded from the Plymouth area, England, 10-30 m deep (see Berrill, 194 7, 1950;Carlisle, 1953) and off Morocco, 110-490 m (Peres, 1959), all quite far apart from Romanov's locality in the Japan Sea. Consequently Romanov's record is questionable.…”

Les Didemnidae (Prochordata) d'Helgoland

“…Leptoclinum rnaculosurn (MILNE EDWARDS 1841), Didemnum candidum (HART-MEYER 1906, CARLISLE 1954, LAFARGUE 1968, MEDIONI 1970, Didemnurn ,helgolandicure (MICHAELSEN 1921).…”