250 Notes on Biatomaeese. V'Z\}l^XT^"^} 



and yet the use of tlie highest powers of the microscope has failed 

 to detect the means of their union into one mass or composite group 

 of individuals. This grouping of individuals together, which we so 

 commonly find among the Diatomacese, as in Schizonenia, Ach- 

 nanthes, Melosira, and a host of other genera, appears to me to 

 have its analogue in the animal kingdom in the Polyzoa ; which, 

 although generally fixed, yet at certain periods throw oif motile 

 forms by means of which the species is clistributed. Do not the 

 DiatomaceaB do likewise ? I am of opinion that they do, and I 

 shall produce evidence on that point farther on. As to the Bacil- 

 laria j)aradoxa, the oftener I watch it the more it puzzles me. 

 Not long since I saw one specimen (of course I mean one bundle 

 of individuals) slide out to its utmost limit across the field of view, 

 and then, becoming entangled with two others, which likewise were 

 made up of many individuals, some eight or ten of its frustules (as 

 the complete individuals are called) were twisted around almost off 

 from the rest, so as to lie at right angles to them, and when the 

 group containing the largest number of frustules receded to their 

 former position, which they soon did, the eight or ten seeming by 

 the act of twisting to lose their power of motion among themselves 

 for the time being, were dragged along in a helpless condition, and 

 twisted completely around one revolution, so as thereafter to fall 

 back again into their places, when all went on as usual. That is 

 to say, the regular motion of all the frustules over each other suc- 

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

 eccentric movement ! As I have already said, I am more puzzled 

 than ever. 



For some time back a discussion has been taking place in some 

 of the European journals as to whether this j)lant 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 Eiver 

 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 appreciable 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. — Paper read before the Boston Society of 

 Natural History, February 9th. 



(To be continued in our next No.) 



