Lessons in elementary biology / by T. Jeffery Parker.

  • Thomas Jeffery Parker
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: Lessons in elementary biology / by T. Jeffery Parker. Source: Wellcome Collection.

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    organism. 'These are small ovoidal structures (.\, pyr.), with clearly defined outlines occurring in varying numbers in the chromatophorcs. When treated with iodine they assume a dceji, apparently black but really dark blue, colour. The assum])tion of a blue colour with iodine is the characteristic test of the well-known substance starch, as can be seen by letting a few clrojis of a weak solution of iodine fall upon some ordinary washing starch. 'The bodies in question have been found to consist of a proteid substance covered with a layer of starch, and are called pyrenoids. Starch itself is a definite chemical com])otmd belonging to the group of carbo-hydrates, i.e., bodies containing the elements carbon, hydrogen, and oxygen : its formula is Cr, In Htematococcus pluvialis there is no contractile vacuole, but in another species, IP. lacustris, this structure is pre- sent as a minute space near the anterior or jioinled end (Fig. 3, K, 0 vac). 'There is still another characteristic structure to which no reference has yet been made. 'This appears at the first view something like a delicate haze around the red or green body, but by careful focusing is seen to be really an extremely thin globular shell (a, c w.) composed of some colourless trans- ])arcnt material and separated, by a space containing water, from the body, to which it is connected by very delicate radiating strands of protoplasm. It is perforated by two extremely minute apertures for the passage of the flagella. Obviously we may consider this shell as a cyst or cell- wall differing from that of an encysted .Amceba (Fig. i, u) in not being in close contact with the jirotoplasm. A more important difference, however, lies in its chemical com|)Osition. 'The cyst or cell-wall of Anneba, as stated in the preceding lesson (p. ii) is very probably nitrogenous :
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