Attack of the timber specimens was much less severe in the laboratory than in some marine localities. This is not surprising. One reason is certainly that wood-boring molluscs (Teredinidae and Pholodidae) which were missing in the laboratory are the most important wood-destroying organisms in the open sea. Another reason is that it is not possible to offer the gribbles optimal environmental conditions. The amount of water is too limited in the laboratory. But a rating of the timber specimens was possible also in the laboratory. It will be compared now whether this rating corresponds to the results at the different geographical sites. In Genoa and La Rochelle the wood specimens were too poorly infested in the beginning to allow any rating (from the results known to me). Angélique was heavily attacked at all the other stations (Vancouver, Follonica, Sekondi, Naos Island), Aniegré at least at Follonica and Naos Island. Aniegré was not tested at Sekondi and proved to be more resistant at Vancouver. Moabi was heavily attacked - also by Limnoria - only at Sekondi and showed medium and slight Limnoria attack at Follonica and La Rochelle, while it was resistant at Naos Island and Vancouver. Cocobolo, only tested at Follonica and Vancouver, proved to be not resistant. Bilinga was heavily infested at Follonica and Sekondi. All the other timber species which proved to be resistant in the laboratory test with Limnoria failed at least at one of the stations named, except Laurel negro (not tested at the tropical stations) and Cedro espino (obviously only tested in Follonica). But Makoré, Douka, Wacapou and Congotali were satisfactorily resistant at the non-tropical stations. Only Guayacan, Mukulungu and Azobé failed also there. Mukulungu also by Limnoria attack and Azobé only by attack of molluscs. From these results it can be concluded that it will not be possible to predict a good natural durability in the sea from the experience of one or of a few test sites only. On the other hand it is obvious that those timber species which show medium or slight attack already in the laboratory will fail in the sea. Thus a laboratory test will be valuable as a screening test in order to exclude unsuitable species but it will not be sufficient to guarantee good resistance under practical conditions.

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