Smithsonian miscellaneous collections . nimal organisms. Butthese tiny crafts move without oar or sail, paddle-wheel or apparently present the anomaly of moving- without any organof locomotion! Many theories have been invented to explain thismystery; as fine protruded pseudopodia (Ehrenberg), osmotic cur-rents of water (Naegh and H. L. Smith), rows of cilia (J. D. Cox),a stream of protoplasm moving along the raphe a line on eachvalve, generally in the middle that is thought to be a narrow cleft(Muller). But none of these fit the case. No method of stainingknown has been able to
Smithsonian miscellaneous collections . nimal organisms. Butthese tiny crafts move without oar or sail, paddle-wheel or apparently present the anomaly of moving- without any organof locomotion! Many theories have been invented to explain thismystery; as fine protruded pseudopodia (Ehrenberg), osmotic cur-rents of water (Naegh and H. L. Smith), rows of cilia (J. D. Cox),a stream of protoplasm moving along the raphe a line on eachvalve, generally in the middle that is thought to be a narrow cleft(Muller). But none of these fit the case. No method of stainingknown has been able to show any protrusions. Whatever be thefinal explanation, it must explain not swimming but creeping; forthese organisms are perfectly inert and helpless unless in contactwith some fixed surface. This alone disposes of all theories requir-ing cilia, flagellse, osmotic currents, etc. The power, too, must beconsiderable ; for will push aside in their course inert mat-ter many times their bulk. The theory must also apply to the ends. Fig. 16. of the frustules; for the plant will often stand upon end and swingabout most vigorously. It is not at all improbable that the so-calledgelatinous sheath, which overlies uniformly the entire externalsurface and is connected with the living cell contents throughnumerous minute pores, is the seat of this motion, and by undulatorymovements over its surface produces the phenomenon that is soevident and so puzzling. Any one who will watch the strange ac-cordeon-like extending and retracting movements of those well-named diatoms, Bacillaria paradoxa, especially when, fully extended,they touch each other only at the tips and yet form a series as rigidas a rod, will see that some explanation based on the external mem-brane fits the case better than any other. See Fig. 16, A and B. A few words should be said upon the practical uses of the first of these is as polishing powders. Under the name of tri- MANN] DIATOMS, THE JEWELS OF THE
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
