Giant clams (family Tridacnidae) are special in that they contain large numbers of symbiotic dinoflagellates, Symbiodinium sp., commonly called zooxanthellae which live in the clam's siphonal mantle (hypertrophied siphonal tissues) (1) and are important in its nutrition (2, 3). In 1946, Mansour (4) partially described a tubular system arising from the clam stomach, extending into the mantle and containing zooxanthellae. However, the eminent scientist Sir Maurice Yonge (5, 6) disputed its existence. Subsequently, Yonge's views appear to have suppressed further investigations of Mansour's observations. The zooxanthellae have been universally regarded as living in the hemal spaces of the mantle (2, 5, 7, 8, 9). This study, however, has conhrmed the presence of the tubular system indicated by Mansour and has shown that the zooxanthellae live within a branched, tubular structure that has no direct connection with the hemolymph. The existence of this tubular system has important implications for our understanding of the symbiosis between tridacnids and their symbiotic algae.

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The effects in goats of the subcutaneous injection of varying doses of Pseudomonas pseudomallei (90 to 500,000 bacilli) suspended in normal saline are described. High doses (greater than or equal to 500 bacilli) caused acute, fatal infections. Lower doses (90 to 225 bacilli) caused acute or chronic disease when infection became established. However, 11 of 18 goats injected with the lower doses of bacilli showed no sign of infection on clinical or bacteriological examination. Response to antibiotic therapy with long acting tetracycline and chloramphenicol was minimal. Goats surviving the initial phase of infection tended to overcome the disease with a corresponding increase in the number of abscesses that were sterile at necropsy. In infected goats, clinical signs included undulating fever, wasting, anorexia, paresis of the hind legs, severe mastitis and abortion. At necropsy, abscesses were found predominantly in the spleen, lungs, subcutaneous injection site and its draining lymph node.