History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard.

  • Andrew Pritchard
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    34/1074 (page 14)
    The coiipling of the fronds generally takes place from the convex margin, but may occur on the concave, or even the convex margin of one frond may couple with the concave of the other. _ The Rev W Smith (A. N. H. 1850) represents the conjugation ot Closterium 'Ehrmbergii to be pecuHar (XVI. 11, 12, 13, 14) The &st Tjhenomenon (he tells us) is an alteration in the granular condition of the endochi-ome. This, from a Hght yeUowish green, passes to a^ much darker shade, and the larger granules, or diaphanous vesicles of Ealis, which were originaUy few in number, and arranged in a somewhat irregular longi- tudinal series (XVI. 10), become exceedingly numerous and pervade the entire frond. We this change is about taking place, the fronds approach in paii-s, approximating by theii- concave siufaces, and finaUy coming into such close neighbourhood that their inflated centres are m contact and their extremities shghtly overlapped (XVI. 11). In a short time probably in the course of twenty-four hours, a remarkable change takes place, both m the appearance and condition of the fronds ; a mass of dehcate mucus is secreted around the approximated fronds ; these remove to a httle distance from each other, undergo seK-division, and present altogether an m-egular oval figiire, ?he o itUne of wHch is formed by the periphery of the mucus the foiir di^a- sions of the fronds being placed in the middle in a somewhat quadnlateral manner (XVI 12). Dming the progress of ceU-division, the internal mem- brane of the ceU-wall becomes enlarged at the suttu-e or hue of separation, aS projects in the form of an irregular cone, with a blunt or rounded apex foning a beak, whose side view presents a triangtilar outhne. This beak beXies filled ^th endochrome, either by the dilatation or increase of the coSts of the haJf-fi-ond, and the divided frond assumes the appearance of one S two unequal segments (12), being what M. Moi-ren caUs ' a C os- ieriZ of two unequal cones. On these membranous expansions at the con- cave sui-faces of the fronds, and close to the ongmal sutoes, there appear, atoosSiltaneously with the formation of the beaks two cuxular projec- t's Xt, rupturing at their apices, give egress to the dehcate sacs which endosrthe endochrome, and wHch, drawing with them theu- contents and meeSg w^th the endochrome sacs emitted through similar projections from fnm'ilv ^v delScence at the centml transverse sutui-e, and the consequent ScenL ofTe contents of the two ceUs into a roimded or r oS^ation which talhes witii the acco.^t P-n^ -^^^ membrane [and] the -P-^^ ^^^^ out of the mere of the contents ^l^thed by the mt^^f^^^^^^^ ^^J^ contents as a new ceU mside the lother cOh ^^^^^J membrane, Desmidiese, the conjugating ^^^^^'Xc^^^^^^ out of the mere unite through the inner; the h^^^^^eU;^^ By the fii^t-named contents as a new cell mside t^^^^J^^^^^^^^^^^ . ^ot^ direct result of