sxi. OYSTERS. 305 



the lashing of the invisible gill-hairs a current of water is 

 set up which partly sweeps upwards along the gill-plates 

 to the vestibule, and partly passes in at the slit-like gill- 

 meshes, and thus through their spongy and tubular structure 

 into the posterior chamber. Thus through the edges of 

 the shell, and between the mouth margins, a constant 

 current passes inwards ; while an equally constant current 

 passes outwards through the posterior chamber. The 

 blood in the gills is thus aerated ; the ejecta from the 

 alimentary canal (and also the kidney) are swept out ; 

 and at the same time food-bearing water is carried to the 

 vestibule where the myriad transparent hairs which cover 

 the " moustaches " sweep the unsuspecting minutiae into 

 the slit-like mouth. 



I often wonder whether so tasty a morsel as the oyster 

 itself possesses a sense of taste. Were Nature just, this 

 sense should be well developed. One would fain hope that 

 our sapid friend's fleshy moustachios may minister to taste ; 

 that for him too there may be some gleams of " gustatory 

 summer lightning." As a hope, however, it must remain : 

 there is no conclusive evidence that the oyster possesses a 

 sense of taste. Indeed it does not appear that Nature has 

 been in any way lavish towards the oyster, in the matter 

 of sensory endowments. Its sense of hearing has gone 

 along with the foot, in which organ the auditory sac is 

 lodged in less sedentary rnollusks. Smell, or rather some 

 sense by means of which it can test the incoming water, it 

 may have. A sense of touch, distributed especially, it may 

 be, along the mantle-fringe, is undoubtedly present. There 

 are no eyes ; but the dusky-coloured mantle-fringe is 

 probably vaguely sensitive to light. For when the shadow 

 of an approaching boat is thrown on to a bed of oysters 

 they are said to close their valves before any undulation of 

 the water can have reached them ! 



