Mr. A. W. E. O^Shaughnessy on Green Oysters. 225 



and which, when thus collected together in a lump, became 

 visible to the naked eye. He says that, on placing a drop of 

 the water under the microscope, he perceived thousands of 

 Vibrios sporting about with every possible kind of motion — 

 sometimes with a sudden jerk or impulsion forwards or back- 

 wards, sometimes spinning round on their own axis like the 

 needle of a compass, sometimes standing straight up on one 

 end, or darting off with astonishing velocity at some other ani- 

 malcule, and sticking one of their pointed extremities into him 

 as if it were a lance. 



That the green colour which makes its appearance in the 

 oyster is really due to the absorption of these living atoms, M. 

 Gaillon has expressed his firm conviction, both in the ' Journal 

 de Physique^ above cited, and in the ^Memoirs of the Linnsean 

 Society of Calvados.' He assures us that as soon as the fresh 

 water is again allowed to have free access to the reservoir the 

 oysters gradually lose both the green hue and the altered flavour 

 which accompanies it, although they are sometimes so thoroughly 

 impregnated with the green matter that they do not quite lose 

 it even in the winter, consequently long after the disappearance 

 of the Vibrios ; there is, however, a gradual and sensible dimi- 

 nution in the tint. It is this duration of the green colour so 

 long after the animalcules have ceased to exist, says M. Gaillon, 

 which accounts for the assertion that green oysters may be ob- 

 tained all the year round; those, he observes, who have never 

 witnessed the intensity of the colour at certain seasons of the 

 year would probably designate as green oysters any which showed 

 the faintest remnant of that tint. 



According to all observers, it is the region of the branchiae or 

 gills which exhibits this peculiarity the most strikingly. Now 

 M. Gaillon assures us, from having examined these organs with 

 the microscope, and compared the orifices of the tubular fila- 

 ments with the size of the animalcules, that the latter could not 

 possibly enter the system of the oyster in that region. 



Perhaps one of the most significant facts recorded by M. 

 Gaillon as the result of his laborious observations is, that at dif- 

 ferent seasons of the year the water of the oyster-" parks " pre- 

 sents very different tints, being sometimes brown, at others 

 green or yellow — both the brown and the yellow being equally 

 the result of the abundant presence of microscopical animalcules 

 of a different species from the green Vibrio ostreariics. The 

 brown species, we are told, has as striking an effect on the colour 

 of the oyster as the green one, and greatly improves its flavour ; 

 whereas the yellow are considered prejudicial. 



With reference to these so-called animalcules, we need scarcely 

 state that the atoms hitherto referred to the genus Vibrio are 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. xviii. 1 6 



