524 ORIGIN OF SPECIES 



start from a common origin. If we look even to the two 

 main divisions — namely, to the animal and vegetable king- 

 doms — certain low forms are so far intermediate in character 

 that naturalists have disputed to which kingdom they should 

 be referred. As Professor Asa Gray has remarked, "the 

 spores and other reproductive bodies of many of the lower 

 algas may claim to have first a characteristically animal, 

 and then an unequivocal vegetable existence." Therefore, 

 on the principle of natural selection with divergence of char- 

 acter, it does not seem incredible that, from some such low 

 and intermediate form, both animals and plants may have 

 been developed; and, if we admit this, we must likewise ad- 

 mit that all the organic beings which have ever lived on this 

 earth may be descended from some one primordial form. 

 But this inference is chiefly grounded on analogy, and it is 

 immaterial whether or not it be accepted. No doubt it is 

 possible, as Mr. G. H. Lewes has urged, that at the first 

 commencement of life many different forms were evolved; 

 but if so, we may conclude that only a very few have left 

 modified descendants. For, as I have recently remarked in 

 regard to the members of each great kingdom, such as the 

 Vertebrata, Articulata, &c., we have distinct evidence in 

 their embryological, homologous, and rudimentary structures, 

 that within each kingdom all the members are descended 

 from a single progenitor. 



When the views advanced by me in this volume, and by 

 Mr. Wallace, or when analogous views on the origin of spe- 

 cies are generally admitted, we can dimly foresee that there 

 will be a considerable revolution in natural history. Sys- 

 tematists will be able to pursue their labours as at present; 

 but they will not be incessantly haunted by the shadowy 

 doubt whether this or that form be a true species. This, I 

 feel sure and I speak after experience, will be no slight re- 

 lief. The endless disputes whether or not some fifty species 

 of British brambles are good species will cease. Systematists 

 will have only to decide (not that this will be easy) whether 

 any form be sufficiently constant and distinct from other 

 forms, to be capable of definition; and if definable, whether 

 the differences be sufficiently important to deserve a specific 

 name. This latter point will become a far more essential 



