. L'évolution et la fonction de la matière vivante purposve . sed ina membrane pendant la plus grande partie de son existence ; la substance du noyau étant formée de l'ameshwork de protoplasme différencié ou linine, Holdingin ses filets granules d'une substance connue asChromatotine que de nombreux biologistes considèrent comme la substance de base des caractères héréditaires. Mais nous avons expliqué, les bactéries et algue inférieure, qui forment de vastes et les classes les plus importantes d'êtres ne possèdent pas un noyau ou une chromatine entièrement formée, néanmoins ils constituent les classes les plus nombreuses et prolifiques de bein

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. The evolution and function of living purposive matter . sed ina membrane during the greater part of its existence ;the substance of the nucleus being formed of ameshwork of differentiated protoplasm or linin, holdingin its meshes granules of a substance known asChromatin which many biologists consider constitutesthe basis substance of hereditary characters. But aswe have explained, the bacteria and lower algse, whichform vast and most important classes of beings do notpossess either a nucleus or fully formed chromatin, nevertheless they constitute the most numerous andprolific classes of beings on the face of the earth. LIVING PROTOPLASM 157 Under the microscope the jelly-like protoplasm ofa dead cell appears to be formed of a network ofgranular fibrillse ; but the details of the structure ofliving protoplasm is not so obvious ; and any attemptto gain an insight into the mode of its physiologicalactivities from its apparent structure is useless. Wemust seek the source of these activities in its ultra TTfLCTosomes. TilMti fdS—, ci/to/>u. — nuclearu/Ltk U niTU-net--work St. ckronuitin/jfanUies va.CijuoltS /cytoHa.sni.1 Fio. 18.—Diagram of a cell. microscopic organisation, accepting the fact, that whatappears to be an homogeneous substance is a complexmixture of elements, which within certain limits, undergo structural re-arrangement through the actionof various forces. Modifications of the structuralarrangement of the elements of living matter thusinduced are accompanied by modifications in itsfunctions, which in the course of time becomehereditary characters. 158 THE NATTIRE OF It is generally admitted that the changes in formand function of living protoplasm such as those towhich we have referred, are attributable to the greatsize and complexity of its proteid molecules.^ Eachof these molecules are supposed to contain from tento thirty thousand atoms, whereas the most complexmolecule known to the organic chemist consists ofless than a hundred atoms. The un

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