The science of life : fully illustrated in tone and line and including many diagrams, S. 303

HOW INDIVIDUALS ORIGINATE

into his children generally survived the rest of him. And a small part of him, growing into his grandchildren, survived still longer. Indeed, unless a man is childless, he does not wholly die. A bit of him, part of his living substance, is handed on, generation after generation, for ever.

For this immortal bit of the organism, that is to live on after the rest is done with, Weismann coined the phrase germ-plasm. He set it in contrast to the soma, which is the mortal remainder. More than 99:9 per cent. by weight of the reader is soma; a fraction of an ounce of material in his testes or her ovaries is germ-plasm. The soma is the individual who will live and die ; the germ-plasm may go on indefinitely.

The germ-plasm is potentially immortal. Generation after generation it lives on, sprouting out bodies to house it and feed

it and keep it warm, driving them with strange appetites and lusts so that it may get release from them and start again. Clearly it is the germ-plasm which evolves, not the ephemeral individual bodies that it throws out. The horse evolution was a_ slow modification of equine germ-plasm ;_ the Micraster evolution a steady change in seaurchin germ-plasm ; man’s rise from the apes is also a stir in the germ-plasm.

For in a sense there is only one germplasm. Presumably life had a single origin ; the living things we know to-day are divergent branches of one stock, twigs of one tree of germ-plasm. In the frame of space-time there is actual material continuity between Mr. Everyman, his wife, his cat, and his aspidistra.

On the workings of this germ-plasm we must for a while concentrate our attention.