What properties are essential to a medium capable of transmitting wave motion? Roughly, we may say two: elasticity and inertia. - Oliver Lodge

A body can only act immediately on what it is in contact with; it must be by the action of contiguous particles—that is, practically, through a continuous medium, that force can be transmitted across space.

All we know at present of locomotion is the locomotion of one piece of matter with reference to other pieces. That can be freely granted, and the whole edifice of physics is consistent with the idea that locomotion through the ether is impossible to measure. But the impossibility has never been proved, and some day an exceptional phenomenon may be found.

It is not the germ cell itself, but the bodily accretion or appendage, which is abandoned by life, and which accordingly, dies and decays.