1881.] 



MICROSCOPICAL JOURNAL. 



6Y 



I 



sions of coloring matter which were 

 conducted in a similar way to those 

 made some years ago by Prof. H. L. 

 Smith with indigo.* Prof. Smith 

 noticed that particles of indigo in 

 suspension in the water were moved 

 along the raphe of the living diatom, 

 sometimes collecting in a ball at the 

 central nodule, and, again, running 

 along to the end of the frustule, were 

 broken and scattered in a rather sym- 

 metrical cloud about the extremity 

 of the shell. The later observer 

 has not noted the formation of a ball, 

 or the motion along the raphe, but 

 has reported the cloud-like aggrega- 

 tion of particles, and drawn from the 

 phenomena he witnessed, the conclu- 

 sion that the cause of motion of the 

 diatom is the exosmose and endos- 

 mose of fluid. 



Before any satisfactory solution of 

 the problem can be reached, or any 

 decisive determination whether the 

 motion be due to osmotic or to cili- 

 ary action, a good deal of patient ob- 

 servation must be made, — both of the 

 motion itself under varying circum- 

 stances, and of the structure of the 

 diatom, including the nature of the 

 raphe itself and the question of the 

 existence of a gelatinous envelope cov- 

 ering free as well as stipitate frustules. 



The following observations, which 

 have recently been repeated and 

 fully verified, are copied from 

 notes made in the Summer of 

 1879, and are a contribution to 

 the record of facts which any sound 

 theory on the subject must account 

 for. They certainly seem most con- 

 sistent with a supposition -of ciliary 

 action, though it is possible that 

 some form of osmotic action might 

 produce similar phenomena. 



A fresh gathering of diatoms from 

 a little brook near Cincinnati, con- 

 tained a number of Nitzschia linearis^ 

 which had progressed so far in self- 

 division that the front view of the 

 frustule was twice as broad as the 

 side view, but from the peculiar form 



* This Journal, Vol. I, p. 183. 



of the Nitzschia the carina was in 

 plain view on each edge of the frustule 

 as it lay or moved on its broader side. 

 The first case I noticed was that of a 

 frustule apparently held fast by the 

 glasses of the compressor, but a gela- 

 tinous mass of decomposed vegetable 

 matter was seen moving steadily 

 along the frustules from one end to 

 the other, making a momentary halt 

 in the middle. The mass was as 

 large in diameter as the width of 

 the diatom, so that it reached from 

 side to side of the frustule, overlap- 

 ping the carina of the valve on 

 one side. The motion of the loose 

 matter was once or twice reversed, as 

 if the diatom was trying to back out 

 of its position, and so produced a 

 current in the opposite direction. 

 Presently the diatom got loose, backed 

 out and moved a considerable dis- 

 tance across the field, the gelatinous 

 substance still adhering and being 

 dragged after it. Again an obstruc- 

 tion was met, the diatom stopped, 

 and as if the machine were reversed 

 in the new effort to back out, the 

 foreign matter was again dragged 

 to the foremost end, and this time a 

 smaller floating particle of similar 

 kind moved in the same manner 

 along the opposite valve of the frus- 

 tule. In an effort to make the dia- 

 tom roll over, so as to enable me to 

 make more sure of its species, it was 

 swept out of sight and lost. 



A little later some fresh samples of 

 similar material afforded a repetition 

 of the phenomena and confirmation 

 of the facts. A frustule of the 

 same species as the former was so 

 wedged in the compressor that one 

 end was free, whilst the other was 

 fast. The free end would move 

 vigorously oneway or the other, in an 

 arc of a circle, but the diatom was 

 not released. Attached to it were 

 two gelatinous masses, one on each 

 side, and of similar size to those de- 

 scribed in the former case. These 

 were distinctly applied to the valves 

 so that, as the diatom lay in front view, 

 as before, the two masses were on the 



