Evolution / by Patrick Geddes and J. Arthur Thomson.

  • Patrick Geddes
Date:
[1911?]
Catalogue details

Licence: Public Domain Mark

Credit: Evolution / by Patrick Geddes and J. Arthur Thomson. Source: Wellcome Collection.

    90/264 (page 86)
    The Beginning of a Body.—The simplest organisms are single cells physiologically com¬ plete in themselves; they leave off where higher creatures begin, that is to say, in a unicellular state; they do not form “bodies.” Here we have perhaps the greatest gap and the greatest step in organic nature, that between single-celled and many-celled organ¬ isms. It is very interesting to inquire into the beginning of a “ body.” What are the possibilities ? We know of some simple units that have a habit of coalescing into composite masses, of others in which the nucleus divides over and over again within the cell so that multi- nucleate organisms are formed, and of others again that break their definition, and do their best to get beyond the unicellular state, by forming loose colonies. It was probably in the third of these ways that body-making began. Certain simple organisms, unable fully to complete that division into two or more separate units which normally occurs at the limit of growth, bridged what Agassiz called “ the greatest gulf in organic nature.” It was perhaps through some weakness that the daughter-units, formed by division of the mother-cell, remained associated, instead of drifting apart in individual completeness.