Identifier: microscopeitsrev00carp (find matches)
Title: The microscope and its revelations
Year: 1901 (1900s)
Authors: Carpenter, William Benjamin, 1813-1885 Dallinger, W. H. (William Henry), 1842-1909
Subjects: Microscopy Microscopes Natural history
Publisher: Philadelphia, P. Blackiston's Sons and Co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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which the two valves, although equal, yet constantlyunite in such a way that the similar parts alternate with oneanother, as may be seen in Asteroktmpra. That it is impossible forbinary subdivision to take place in these three classes of forms. i>confirmed by the fact that, notwithstanding that there are recordednot less than seventy-five observations of the process of division inthem, not one affords an exception to the rule given above. Where multiplication by binary subdivision occurs among theDiatomacece, it takes place on the same general plan as in the Des-inidiacece, but with some modifications incident to peculiarities ofthe structure of the former group. The first stage consists in theelongation of the cell, and the formation of a hoop adherent to 1 See Castracane, The Theory of the Eeproduction of Diatoms, Atti dell Accad.Pontif. del Ni/ori, Lhicci, May 31, 1874; and New Arguments to prove thatDiatoms are reproduced by means of Germs, ibid. March 19, 1870. g Q 2 PLATE XII
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ARACHNOIDISCUS JAPONIC is. .• DIATOMACEJS 597 continued connection of the two frustules by its means gives rise toan appearance of two complete frustules having been developedwithin the original (fig. 445, A, C) ; subsequently, however, the twonew frustules slip out of the hoop, which then becomes completelydetached. The same thing happens with many other diatoms, sothat the hoops are to be found in large numbers in the settlings ofwater in which these plants have long been growing. But in some other cases all trace of the hoop is lost, so that itmay be questioned whether it has ever been properly silicified, andwhether it does not become fused (as it were) into the gelatinousenvelope. During the healthy life of the diatom l the process ofbinary division is continually being repeated ; and a very rapidmultiplication of frustules thus takes place, all of which must beconsidered to be repetitions of one and the same individual form.Hence it may happen that myriads of frustules maybe f

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