90 THE NAUTILUS. 



sel was exhausted, the shell relax, when the juices would be with- 

 drawn, after which the animal would die. 



On further enquiry I could find no one that had ever caught 

 Mr. Catfish in the act, and I was not altogether satisfied with this 

 theory. 



This lake, in common with the Illinois, Mississippi and nearly all 

 of the western rivers, is at lower ebb than ever before known in the 

 history of the country. From accounts in the daily papers there is 

 great mortality among the fish of the INIississippi River, and immense 

 numbers ai'e dying as a result of this low water. 



Might not this be the cause of the death of the mollusks in this 

 lake ? Is the same phenomena observed in other bodies of water ? 

 Let us hear from other points. Or, have the catfish in this lake, 

 like an egg-sucking dog, learned a trick and are making the most 

 of it. 



ON THE BYSSUS OF UNIONID^S:. II. 



BY DR. V. STERKI. 



Some time since I succeeded, not without hard Avork, in finding 

 three more specimens of Unio with a byssus, one U. luteolus Lam., 

 15 mm. long, one U. (prob.) ligamentmus, only 9 mm. long, and U. f 

 8 mm. Unfortunately I had not leisure to make an examination as 

 exact as I wished ; yet to my account in the last Nautilus I can add 

 the following: the threads were for the most part colorless, or only 

 slightly brownish. On the parts examined I found the cortical layer 

 little developed. The byssus were more or less branched ; on a piece of 

 one about three inches long, I counted seven branches. Of the forma- 

 tion of these I can give an idea best by comparing them with a grass 

 stalk : the branches sjirung out from like leaves Avith short sheath, the 

 latter with circularly arranged fibres, apparently not derived from 

 the inner part of the " stem," but at a short distance, the branch, first 

 flat, like a leaf, further off growing more or less cylindrical, was 

 entirely composed of longitudinal fibres, Avhich consequently are 

 formed for themselves by apposition and the main thread is not 

 sjilit. 



Later I had a chance to get some other very young mussels, among 

 which Avas one only 3"5 mm. long, the smallest I have found so far, 



