440 NATURAL SCIENCE. August. 



with living forms. In these beds, as in the ooze of existing seas, the 

 invariable presence of large numbers of uninjured shells seems to 

 point to protoplasmic death as having at least a possible place in 

 protozoa. But existing protozoa as other existing animals are the 

 direct descendants of the protozoa of long ago. They have established 

 a weighty claim to be considered conditionally immortal. They 

 enjoy two special advantages. By living singly they stand or fall by 

 their own luck ; they are not tied to the accidents of other cells in a 

 cell-commonwealth. Their easier contact with external media, and 

 readier means of getting rid of waste products, or of accidentally- 

 taken dangerous substances, makes them less subject to the intrinsic 

 accidents associated with cell-life. 



Germ cells, again, unlike the working cells of the body, lie com- 

 paratively dormant within the tissues until the time comes for the 

 playing of their own part. Practically all the ova a woman produces 

 are already formed in the newborn babe. They lie in the ovary, 

 secluded from the wear and tear of cell-life, subject to few dangers, 

 and as far from the vicissitudes of somatic life as possible. And, 

 lastly, the invariable extrusion of at least one polar body from every 

 ovum is a mysterious and unique condition ; a condition which may 

 be a special effort to remove from the cell bye-products the slow 

 accumulation of which in tissue-cells ultimately causes disease or 

 disturbance. 



We know that all other cells do ultimately die, and that death of 

 all kinds can be reduced to cell-death. The meaning of cell-death 

 and the meaning of cell-life will be discovered together. But already 

 we know something of the processes going on in living cells. In the 

 first place there is decomposition. We cannot trace all the details, 

 but we know that a number of substances are taken in, so to speak, 

 at one end, and that a number emerge at the other. It is futile to 

 say that the processes are not the processes of chemistry, as we do 

 not know the constitutional formulae of many of the substances which 

 enter or emerge. But the sum of the activity is a slow feeding of 

 substances of a high potential ; a complicated flux of these within the 

 cell ; and an emergence of substances of a lower potential. Clearly 

 there are a large number of ways in which such a process can be dis- 

 arranged. A sudden stimulus may set off the liberation of energy so 

 rapidly that there is none left to do the work of bringing in more food, 

 and starting the chemical reactions. Some waste substance produced 

 accidentally or usually in small quantities, and not regularly excreted, 

 may slowly accumulate until it clogs the whole action. Even in 

 inorganic chemistry, reactions are often apparently so capricious that 

 we know they must be influenced by a multitude of apparently 

 trifling conditions. Lastly, the introduction of some unwonted 

 substance may arrest or supplant the normal reactions. 



For the elucidation of all these, there is wanted much experi- 

 mental organic chemistry. Above all, there is wanted a careful 



