100 



February 6, 1861. 



The President in tlic Chair. 



Dr. B. J. Jeffries made the following report on a specimen 

 of Ichthin, submitted to him at the last meeting : — 



The fluid was of a pale-yellowish color, consisting, as he under- 

 stood, of Ichthin in a mixture of alcohol and water. From this fluid 

 there was deposited in the bottom of the phial a thin sediment of a 

 light yellowish color. This sediment, examined under the microscope, 

 with a diameter about 250 to 300, proved to consist mostly of little 

 white tables or plates, chiefly of quadrangular forms. The sediment 

 when dried was treated with ivater, which appeared to have no effect 

 on the granules, simply giving them opportunity to move about as 

 regards each other. Alcohol appeared to bring the granules out 

 more distinctly, and they exhibited a tendency to aggregate some- 

 what like blood-corpuscles. It had no other effect as far as could be 

 noticed. Ether, pure, did not affect them. Liquor potassce appeared 

 to break portions of some of them down, and render others more 

 pellucid. Nitric Acid had the same effect to a greater degree. 

 Acetic Acid rendered them more pellucid, and, after they had been 

 treated with it and dried, they appeared to shrink. The action of 

 Hydrochloric Acid was nearly the same. They did not disappear under 

 its effect. Sulphuric Acid rendered them most pellucid, and after a 

 time quite indistinct, so that a dim light was required to bring them out. 

 Some of them were burnt for twenty minutes on a glass, which was 

 kept at a red heat, and had not then disappeared, although most of 

 them were broken down. After they had been subjected to this heat 

 for an hour, they had entirely vanished. 



This ichthin, for so this examination seems to show it to be, was 

 taken from the egg of a ray found at San Francisco. Perhaps the 

 Raia ocidata, Girard. It may be possible, from what MM. Valen- 

 ciennes and Fremy have observed, to distinguish the species of ray 

 from this substance found in the e^ir. 



'oo 



Prof. Agassiz made some observations on the rate of in- 

 crease and other characters of fresh-water shells, Unios. 



To determine their rate of growth he had collected large numbers 

 during every month in the year ; he always found many series of 

 shells of different sizes, all of a size in each series, the whole suite of 

 specimens representing all the intermediate sizes, and, as he believed, 

 the rate of growth and annual increase. Tliough different species 

 breed at different seasons, none breed more than once a yoar, as is 

 proved by examination of the gills in which the eggs are d*»)osited. 

 The small shells, less than an inch long, have generally been regarded 



