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The Nautilus 



Vol. v. NOVEMBER, 1891. No. 7 



A BYSSUS IN TJNIO. 



BY DR. V, STERKI, NEW PHILADELPHIA, OHIO. 



In the early morniug of Oct. 2nd, while collecting "mussels" in 

 the Tuscarawas river, I found a young specimen of Unio ligamentinus 

 Lara., 27 mill, long, with a thread-like byssus 8 inches long, at the 

 distal end attached to a small stone of about 8 mill, diameter. The 

 whole thing was wound up, wrapjied in a paper and put in the 

 pocket. Several hours later, when I had time to look at it, the 

 thread was dry, brittle, and broke, becoming detached from the stone. 

 Thus the object was put in water with some glycerine and carbolic 

 acid, for microscopic examination, for which I found leisure two 

 days later. 



The thread was now rather dark-brown in coloration, while, when 

 fresh, it had shown different shades from horn color to light-brown ; 

 as far as seen in the shell — 4'5 mill. — it still was colorless. Irregularly 

 cylindric or somewhat flattened, it had a diameter varying from 

 0*18-0'26 mill. The distal end, where it had been attached to the 

 stone, was flattened and split into several irregular flat filaments, 

 while the proximal end, which now slipped out of the shell as soon 

 as I laid hold on it with the pincers, was thickened to a short bulb of 

 0'42 mill, in diameter. 



The inner or main part of this byssus is composed of hundreds of 

 finest fibres, of different diameters from about 0"0015-0'007 ; but 

 many of them still show more or less distinct longitudinal striation. 

 Even at the proximal or bulb end I could not see any other forma- 

 tion. Outside of this cord of fibres there is a cortical layer of a 



