THE BEGINNINGS OF LIFE. 107 



Living together, as they generally do, tenanting the 

 same tufts of moss or the same patches of lichen, they 

 eke out their existence by instalments, instead of enjoy- 

 ing a more or less definite and continuous span of life. 

 And, during their most extreme degrees of desiccation 

 they certainly can have no more title to be looked 

 upon as living things than can the seeds in the cata- 

 combs of Egypt. Though not living, they also retain 

 the potentiality of manifesting Life: and, for each 

 alike, in order that this potentiality may pass into an 

 actuality, the first requisite is water, with which to 

 restore to them that possibility of molecular re-arrange- 

 ments under the influence of incident forces, of which 

 the absence of water had deprived them, and without 

 which Life, in any real sense, is impossible 1 . 



and Free.' Philosophical Transactions, 1866, p. 613-620. With regard 

 to Nematoids I have there said that ' the remarkable tenacity of Life 

 of which we have been speaking is met with only amongst the repre- 

 sentatives of four land and freshwater genera, Tylencbus, Plectus, 

 Aphelenchus, and Cephalobus ; whilst those of all the other genera, except- 

 ing Rhabditis, marine as well as land and freshwater, are rather remark- 

 able for the very opposite characteristic, they being incapable of recovery 

 even after the shortest periods of desiccation.' It was formerly supposed 

 that all the Free Nematoids exhibited this tenacity of Life. 



1 Professor Owen says (Monthly Microscopical Journal, May I, 1869, 

 p. 294), 'There are organisms (Vibrio, Rotifer, Macrobiotus, &c.) which 

 we can devitalize and revitalize devive and revive many times. As 

 the dried animalcule manifests no phenomenon suggesting any idea 

 contributing to form the complex one of " life " in my mind, I regard it 

 to be as completely lifeless as is the drowned man whose breath and 



heat have gone and whose blood has ceased to circulate 



The change of work consequent on drying or drowning forthwith 

 begins to alter relations or " composition," and, in time, to a degree 



