184 DARWINIANA. 



limited, and that the doubtful species are in a feeble 

 minority. This seemed to be true, so long as a genus 

 was imperfectly known, and its species were founded 

 upon few specimens, that is to say, were provisional. 

 Just as we come to know them better, intermediate 

 forms flow in, and doubts as to specific limits aug- 

 ment." 



De Candolle insists, indeed, in this connection, that 

 the higher the rank of the groups, the more definite 

 their limitation, or, in other terms, the fewer the am- 

 biguous or doubtful forms; that genera are more 

 strictly limited than species, tribes than genera, orders 

 than tribes, etc. We are not convinced of this. Often 

 where it has appeared to be so, advancing discovery 

 has brought intermediate forms to light, perplexing to 

 the systematist. " They are mistaken," we think more 

 than one systematic botanist will say," who repeat that 

 the greater part of our natural orders and tribes are 

 absolutely limited," however we may agree that we 

 will limit them. Provisional genera we suppose are 

 proportionally hardly less common than provisional 

 species ; and hundreds of genera are kept up on con- 

 siderations of general propriety or general conven- 

 ience, although well known to shade off into adjacent 

 ones by complete gradations. Somewhat of this greater 

 fixity of higher groups, therefore, is rather apparent 

 than real. On the other hand, that varieties should 

 be less definite than species, follows from the very 

 terms employed. They are ranked as varieties, rather 

 than species, just because of their less definiteness. 



Singular as it may appear, we have heard it denied 

 that spontaneous varieties occur. De Candolle makes 



