OYSTERS AND METHODS OF OYSTER-CULTURE. 333 



organic matter, and thus interfere greatly with the life and healthy development of 

 the emhryos. 



By our method the objectionable features of the old plan, as stated above, are 

 overcome. If possible select good-sized oysters; open them with the greatest possi- 

 ble care so as not to mutilate the mantle and soft parts. Carefully insert an oyster 

 knife between the edges of the valves and cut the great adductor muscle as close as 

 possible to the valve which you intend to remove, leaving the animal attached to 

 the other valve, which, if possible, should be the left or deepest one. The soft parts 

 being firmly fixed or held fast by the great adductor muscle to the left valve pre- 

 vents the animal from slipping under the end of the pipette, held flatwise, as it is 

 gently and firmly stroked over the generative gland and ducts to force out the 

 generative products. 



To prepare the animals to take the spawn from them after opening, the following 

 precautions are to be observed : Note that the reproductive gland in great part 

 envelops the visceral mass and extends from the heart space, just in front of the 

 great adductor, to within a half inch or so of the head or mouth end of the animal, 

 which lies next to the hinge. Note also that both sides of the visceral mass which 

 incloses the stomach, liver, and intestine are enveloped on either side by a membrane 

 which also lies just next the shell and is garnished by a fringe of purplish, sensitive 

 tentacles along its entire border except at the head end, where the mantle of the left 

 aide passes into and is continuous with that of the right side of the animal. The 

 ventral or lowermost side of the animal, anatomically speaking, is marked by the 

 four closely corrugated gill plates or pouches, which are preceded in front by the 

 four palps or lips, but both the gills and palps depend downward between the lower 

 borders of the mantle of the right and left sides. Note, too, that if the mantle is 

 carefully cut and thrown back on the exposed side of the animal between the upper 

 edges of the gills and the lower edge of the cut or exposed end of the great adductor 

 muscle, the lower and hinder blunted end of the visceral mass will be exposed to 

 view. It is on either side of this blunted end of the visceral mass between the upper 

 edge of the gills and lower side of the great muscle that the reproductive glands 

 open almost exactly below the great adductor. From these openings we will after- 

 wards find, if the animal is sexually mature and the operation is properly conducted, 

 that the spawn will be forced out in a vermicular, creamy white stream. But in 

 order to fully expose the reproductive organ we should carefully continue to sever 

 the mantle of one side with a sharp penknife or small scissors some distance forward 

 of the great muscle toward the head, cutting through the mantle just above the 

 upper borders of the gills and following a cavity which lies between the latter and 

 the lower border of the visceral mass. 



A little experience will teach one how far it is necessary to carry this incision of 

 the mantle. For some distance in front of the heart space the mantle is free or 

 detached from the visceral mass and reproductive organ, which lies immediately 

 beneath, and this enables one, if the last-described incision has been properly made, 

 to almost completely expose the one side of the visceral mass and the richly tinted, 

 yellowish-white reproductive gland which constitutes its superficial jiortion. The 

 opening of the gland and its superficial ramifying ducts beiug laid bare on the 

 exposed side of the animal, we are ready to press out the spawn on that side. Before 

 beginning this, however, it is important to observe that the principal duct passes 

 down just along the edge of the visceral mass where the latter l)ounds the heart 

 space, in which the heart may be observed to slowly pulsate, and that this great duct 

 ends somewhere on the surface of the ventral blunted end of the visceral mass (plate i, 

 fig. 2 d). To expose the great or main generative duct it may be necessary to cut 

 through or remove the pericardial membrane which incloses or covers the heart space 

 on the exposed side. If the oyster is sexually mature, the main duct will be observed 

 ti) be distended with spawn, and that, originating from it and branching out over 

 almost the entire surface of the visceral mass, there are minor ducts given ofi", which 



