AKTIFH'IAL I.KT I.D! NC OK OYSTERS. 723 



being very distinctly visible, especially if tin- glass vessel be resting upon a dark ground so as to 

 bring tlic \\liitisli granules into relief. Tin- granules art- nothing more than the ova or eggs of the 

 Oyster, and at once indicate that the individual from which they were obtained is a female. In 

 case the products are male, they break u|t as they mingle with the water into a milky white cloud 

 in which no granules are visible to the naked eye. It is also very iiii|M>rtaiit to observe that as the 

 milt is stirred in the water it breaks up at lirst into long, fleecy white clouds which resemble very 

 strikingly in miniature what are known to meteorologists as cirrus clouds, or, vulgarly, "mare's 

 tails." reminding one of these in the way in which the flue particles of milt give rise to streaks, 

 \\ isps. and libers as it breaks up in the water, without giving rise to any visible granular appear- 

 ance a> o.-eur> in the ease of the female products, but to an opalescent or milky asj>ect. These 

 distinctions, once learned, are so palpable that the novice may as infallibly discriminate the sexes 

 of the O\stcr apart by their aid as can be done by the most skilled biologist with a powerful 

 microscope. 



Tin: iMi'KKGNATiON OF THE EGOS. The method formerly used was to first learn the sex of 

 a number >f adult Oysters with the microscope, then cut out the generative glands with their 

 products and cuop up those of different sexes separately in small dishes with sea-water. This 

 system we may now say is barbarous, because it is crude; large numbers of eggs are destroyed 

 by crushing, or are injured by the rough usage to which they are subjected, and, besides, there is 

 no assurance that the eggs or milt operated with are quite mature. It is also troublesome to free 

 the generative gland from fragments of the liver which help to pollute the water in the incubating 

 vessels with putrescible organic matter, and thus interfere greatly with the life and healthy devel- 

 opment of the embryos. 



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 possible 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 

 jirevents the animal from slipping under the end of the pipette, held flatwise, as it is gently and 

 tirmly 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 

 arc to be observed: Note that the reproductive gland in great part envelopes 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 bead 01 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 side 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 np|H-r edi: the gills and lower 



side of the great muscle that the reproductive glands opeu almost evi.-.ly below tin- -..-.it adductor. 



