Science from an easy chair / by Sir Ray Lankester.

  • Lankester, E. Ray (Edwin Ray), Sir, 1847-1929.
Date:
1916
Catalogue details

Licence: In copyright

Credit: Science from an easy chair / by Sir Ray Lankester. Source: Wellcome Collection.

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    1 XIX THE SIMPLEST LIVING THINGS I IN old times, if one wanted to compare a man to the humblest and simplest of animals, one called him 1 ‘ a worm. But really a worm is a very elaborate creature, with skin, muscles, blood-vessels, kidneys, ■nervous system, pharynx, stomach, and an intestine, :>md is built up bv hundreds of thousands of proto¬ plasmic cells. Shakespeare got nearer the mark when le made one of his uncompromising professional ‘ murderers exclaim, as he stabbed the young Macduff :o the heart, “ What, you egg ! An egg is a single cell or corpuscle of protoplasm, and the simplest living things are of the same structure—mere units, single corpuscles of protoplasm, often less than the one- |:housandth of an inch in diameter, and invisible except with the microscope, though in some cases big enough to be seen by the naked eye as they swim or crawl in i glass of pond-water. Many thousands of kinds of these simplest animals and plants have been carefully recorded, distinguished from one another, and named by naturalists. !j Many of these unicellular animals (or “ Protozoa ) orawl by a curious irregular flowing movement of the viscid tenacious protoplasm of which they consist. There is no firm coat or cell-wall, only the thinnest pellicle on the surface. The Proteus-animalcule (Fig. 36 A) is so called because of its constant change of shape ; it is also called Amoeba on this account. It flows out into broad, sometimes elongated, finger-like processes, of which one or several of different sizes may be formed at the same time, and then quickly disappear as the whole creature moves. Solid particles of food—minute