28 OYSTERS AND DISEASE. 



stated by Carazzi is quite correct, but tiiese are points which were known before. 

 The novel statements are, we beUeve, entirely erroneous, and are the results either of 

 mistaken observations, or inferences from observations. 



He rightly states that the Marennes green oysters may retain their colour for 

 weeks or even months when taken to other waters in which greening does not take 

 place. It is true of our green Marennes oysters, kept for weeks practically without food 

 in tanks in the laboratory. This fact is well known, and has been mentioned by various 

 writers from Bouchon-Brandely, in 1871, onwards ; but does it not tell strongly against 

 Carazzi's own view that the green substance is a nutrient material on its way from the 

 surface epithelium to the liver ? Is it at all likely that, if the green " Marennin " is a 

 nutrient material in process of metabolism, it will remain for months in the superficial 

 tissue (which by Carazzi's hypothesis has just absorbed it) after the source of supply 

 has been removed ? That is very improbable, even admitting Carazzi's statement as to 

 the distribution of the iron-containing Marennin in the superficial cells to be correct ; 

 but we do not admit it. As we have shown above, we have abundant evidence that 

 the green granules are constantly in the " macroblasts," and comparatively rarely in the 

 ciliated epithelium. In fact, in all essential points of structure — the details of which 

 need not be gone over again — we agree with Lankester, Pelseneer, J. Chatin, and 

 De Bruyne, and differ from Carazzi in his criticism of these former authors. 



Moreover, all the observations made by ourselves, and those recorded by others, 

 'on the West Coast of France are in accord with the view that the " greening " depends 

 upon microscopic food-organisms in the sea-water. Bornet and Ad. Chatin showed, in 

 1894, that the greening comes on suddenly in parks at Sables d'Olonne, where it was 

 not present before. The greening, again, only takes place at a certain time of year, 

 usually autumn, which agrees with the periodic distribution of minute organisms. 

 Bouchon-Brandely says that at Marennes it is a common observation that the oysters 

 only become green when the water in the " claires " (ponds) has become green with 

 microscopic plants. It is known at La Tremblade that when a claire is in the greening 

 condition it must not be emptied, as a change of the water might deprive it of its 

 greening properties. Moreover, the greening must be due to the contents of the water, 

 since in the Island of Cuban (La Trinite River) Dr. Gressy has successfully reared 

 green oysters in basins excavated in the solid rock. 



We must call attention to the way in which Carazzi has peremptorily denied * 

 or misrepresented the results of some of the many investigators of molluscan anatomy 

 and physiology with whom he does not agree. For example, he says of Ryder's 

 statement that the ventricular part of the heart may be green, " he is certainly mistaken," 

 &c. We are able, however, to state that Ryder was perfectly correct, and that it is 



* It is perhaps sufficient, as an example of Carazzi's style, to state that after alluding to the work of Lankester, 

 Pelseneer, and others, he makes the sweeping assertion: — " Tutto quel ch' e stato detto finora sulle ostriche verdi 

 e completamente sbagliato, ed e la conseguenza di osservazioni o infondate o malamente interpretate." 



