THE MICROSCOPE. 117 



scope and a scotoscope. For the first I did give him 5I. los. — a 

 great price, but a most curious bauble it is." 



On February 6, 1672, Sir I. Newton communicated to the Royal 

 Society his "design for a microscope by reflection." It consisted of 

 a concave spherical spectrum of metal and an eye-glass which mag- 

 nified the reflected image of any object placed between them in the 

 conjugate focus of the spectrum. He pointed out the proper mode 

 of illuminating objects by artificial light as he describes it, "of any 

 convenient color not too much compounded," viz., mono-chromatic. 



Quite a decided improvement in simple microscopes was made 

 in 1702 by Mr. Wilson. The improvement consisted in a condenser, 

 screw and opposing spring. The former for increasing illumina- 

 tion, the screw-spring for focussing. 



In 17 10 the elder Adams presents his method of making small 

 globules for high magnifiers to the Royal Society. 



About this time Stephen Grey introduced his "poor man's 

 microscope." It consisted of a plate of brass pierced with a small 

 hole, over which, above and below, he placed a drop of water. 



THE PROBOSCIS AND LABIAL PALPS OF THE 

 OYSTER. 



BY H. J. RICE, SC. D. 



The various changes which take place in the growth of the 

 young of the American oyster (Ostrea Virginiana), up to about the 

 time when the young animals cease to be a free-swimming embryo, 

 have been pretty carefully worked out by a number of investigators 

 during the past two or three years, but following the free-swimming 

 condition there is a stage which, so far as I have been able to ascer- 

 tain, has never been described, or at least its significance, or the 

 relation which it sustains to the adult form, pointed out by any 

 who have studied the embryology or habits of this interesting and 

 valuable bivalve. I refer to what may be called the " proboscis' 

 stage of the young animal, or that stage during which the mouth 

 is located at the extremity of a long, slender portion of the alimen- 

 tary canal which projects from the main portion of the body out 

 into the mouth cavity. During the later portion of the free-swim- 

 ming condition the digestive tract is represented by a large stomach 



