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that when the water became foul, as it did by evaporation, 

 the bottom of the ditch was literally covered with their dead 

 bodies. The gathering, however, I have to speak of at the 

 present time was made for the purpose of procuring Diato- 

 maccse, and consisted of specimens of an alga belonging to the 

 genus Enteromorpha, having attached to it more or less firmly 

 numerous Diatomacese and animals. The commonest form 

 of Diatom Avas a CycloteUa, and seemingly fixed in some 

 manner to the Enteromorpha, for it was not shaken off by 

 pretty rough usage. How it was fixed I could not detect ; 

 most likely by means of a mucous envelope of such tenuity 

 that it is not readily seen. 



The next most common form is the truly wonderful, inex- 

 plicable Bacillaria paradoxa, the paradoxical bundle of sticks. 

 Often and often have I spent hours looking at this marvel of 

 nature, the motion without apparent cause or mode, an invisible 

 joint which, as a friend of mine, an engineer, once remarked, 

 would be a fortune to any one who would discover it, for here 

 we have several sticks forming the bundle, moving over each 

 other without separating, and yet the use of the highest powers 

 of the microscope has failed to detect the means of their union 

 into one mass or composite group of individuals. This group- 

 ing of individuals together, which we so commonly find among 

 the Diatomaceae, as in Schizonema, Achnanthes, Melosira, and 

 a host of other genera, appears to me to have its analogue in 

 the animal kingdom in the Polyzoa ; which, although gene- 

 rally fixed, yet at certain periods throw oiF motile forms by 

 means of which the species is distributed. Do not the Dia- 

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

 shall produce evidence on that point further on. As to the 

 Bacillaria paradoxa, 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 indi- 

 viduals, some eight or ten of its frustules (as the complete 

 individuals are called) were twisted round almost ofi" 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 regu- 

 lar motion of all the frustules over each other succeeded. 



