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structure of synthetic magnetite (Fe 3 0 4 ) (ref. 3). It should be noted, however, that while the reduction of the magnetic moment on heating in synthetic magnetite is caused by oxidation to ferric oxide, this is probably not the case with 4.canthopleura haddoni.We also found that the remanence in virgin state of the radula was less than O• l per cent of the maximum remanence (that is 30 EMU/g) in this material. This negates, in our opinion, the speculation that the magnetic material might serve as a guidance device for navigation 1 • We thank Professor S. Shtrikman and Dr H. A . Lowenstam for their interest and critical comments.

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GZVT ACCESSION NO,. RECIPINNT'S CATALOG NUMBER F-INWSC CRDT9 4,TL ES(An Sublil) s. TYPE OF REA'ORT & PERIOD COVERED ITLE(aidSubitf.

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