120 



THE KINGDOM OF MAN 



in fact, that the simplest form of life at present exist- 

 ing is a highly complicated structure a nucleated cell. 

 That does not imply that simpler forms of living matter 

 have not preceded those which we know. We must 

 assume that something more simple and homogeneous 

 than the cell, with its differentiated cell-body or proto- 

 plasm, and its cell kernel or nucleus, has at one time 

 existed. But the various supposed instances of the sur- 

 vival to the present day of such simple living things 

 described by Haeckel and others have one by one yielded 



to improved methods of 

 microscopic examination and 

 proved to be differentiated 

 into nuclear and extra-nuclear 

 substance. 



The question of * spon- 

 taneous generation ' cannot 

 be said to have been seriously 

 revived within these twenty- 

 five years. Our greater know- 

 ledge of minute forms of life, 

 and the conditions under 

 which they can survive, as 

 well as our improved micro- 

 scopes and methods of experi- 

 ment and observation, have made an end of the argu- 

 ments and instances of supposed abiogenesis. The 

 accounts which have been published of 'radiobes,' minute 

 bodies arising in fluids of organic origin when radium 

 salts have been allowed to mix in minute quantities with 

 such fluids, are wanting in precision and detail, but the 

 microscopic particles which appear in the circumstances 

 described seem to be of a nature identical with the minute 

 bodies well known to microscopists and recognised as 



FIG. 36. 



Further stage in the division of 

 the sexual cell drawn in Fig. 35 (e), 

 showing the twelve chromosomes 

 of the two nuclei of the sperm- 

 cells resulting from the division 

 (twelve instead of twenty-four). 



