272 



Now what kind of a joint can it be that permits of such 

 eccentric movement ? As I have aheady said, I am more 

 puzzled than ever. 



For some time back a discussion has been taking pla^e in 

 some of the European journals as to whether this plant be an 

 inhabitant of fresh or brackish water. What I have observed 

 points to the fact that it will live in either. I have collected 

 it in brackish water at Hoboken, N. J. ; my Weehawken 

 collection was from a ditch connecting directly with the salt 

 water of the Hudson River at its mouth, and some years since 

 I gathered it in the sweet fresh water of the Fishkill creek, 

 along with Desmids and other truly fresh-water plants, which, 

 as far as we know, will not live in water containing any ap- 

 preciable amount of salt, and then, also, in winter and under 

 the ice, but nevertheless in an active condition. And I have 

 taken my salt-water Weehawken gathering and diluted it 

 with several times its volume of fresh water, and yet it 

 seems to flourish after many days, and the Bacillaria is 

 apparently more active than when first procured. So, also, 

 the other Diatoms which are present along with it evidently 

 profit by the change, for they have increased rapidly and are 

 in vigorous motion. 



Along with the Bacillaria in the brackish water at Hobo- 

 ken, I found numerous individuals of an Amphora, which I 

 have known in this neighbourhood for many years, and which 

 I considered unnamed as yet. To it I have given the provi- 

 sional name of A. lanceolata, on account of the form of its 

 outline. This genus has always been considered an epiphy- 

 taceous one ; that is to say, one which grows attached to 

 other plants or submerged substances, yet this form was free 

 and in active motion. In fact I think it was one of the 

 most lively Diatoms I ever saw. So another smaller species 

 of Amphora which is common near here, is always, as far as 

 I have noticed, free. Here we have species appearing both 

 in the free and attached conditions, and this is even more 

 strikingly illustrated in Schizonema. 



Bacillaria paradoxa is usually set down as the most rapid 

 in motion of the Diatomacese, its velocity being recorded by 

 Smith, as he measured it, at over one two-hundreth of an 

 inch in a second. This is certainly pretty quick when we 

 consider that the length of the frustule is only '0025 of an 

 inch. But my experience has been that its velocity varies 

 in every degree from that mentioned to perfect rest ; at 

 times some individuals will be in rapid movement, Avhile 

 others are motionless ; and also I have remarked that from 

 sunrise to noon seems to be the period during which, under 



