CH. XI] B. MORPHOLOGICAL 111 



equal. The diagram will serve for the growth of the families under 

 differentiation, in which progress is supposed to work downwards 

 from the original species and genus that began the family, A, B, 

 or C, both species and genus of course being the same plant. As 

 the family grows, it will form new species and genera, and all will 

 on the average survive, so that the now existing family is in each 

 case represented by all the dots under A, B, or C Whether the 

 whole family, if seriously old, survive like this, will depend upon 



Level 1 



C. Cc. Cbb Cb 



CbChbCc C 



Fig. 8. Diagrammatic origin of small, medium and large families under 

 differentiation, to show relative rank of genera in each, which goes more 

 or less with the line 1, 2, 3 etc. upon which they happen to stand. 



what geological or other catastrophes it has met with, and whether 

 any general change may occur in a genus, causing its death, or 

 transforming it, or more probably one of its species, into another 

 genus. The well-known fact that the smell was lost at the same 

 time by all known examples of the common musk, once universal 

 in cottage windows by reason of its sweet scent, shows that 

 though a species may be represented by innumerable individuals, 

 something may happen simultaneously in the internal make-up 

 of all of them. And there is nothing to show that larger mutations 

 than this are not possible. The way in which the successive fossil 

 species of Stratiotes appear in different geological horizons, each 

 specifically different from the preceding one, shows the kind of 



