LAWS OF VARIATION 205 



deafness, or between the tortoise-shell color and the fe- 

 male sex; or in pigeons between their feathered feet and 

 skin between the outer toes, or between the presence 

 of more or less down on the young pigeon when first 

 hatched, with the future color of its plumage; or, again, 

 the relation between the hair and teeth in the naked 

 Turkish dog, though here no doubt homology comes into 

 play? With respect to this latter case of correlation, I 

 think it can hardly be accidental that the two orders of 

 mammals which are most abnormal in their dermal cov- 

 ering, viz., Cetacea (whales) and Edentata (armadillos, 

 scaly ant-eaters, etc.), are likewise on the whole the 

 most abnormal in their teeth; but there are ?o many 

 exceptions to this rule, as Mr. Mivart has remarked, 

 that it ha« little value. 



I knew of no case better adapted to show the impor- 

 tance of the laws of correlation and variation, indepen- 

 dently of utility and therefore of natural selection, than 

 that of the difference between the outer and inner flowers 

 in some Compositous and Umbelliferous plants. Every 

 one is familiar with the difference between the ray and 

 central florets of, for instance, the daisy, and this differ- 

 ence is often accompanied with the partial or complete 

 abortion of the reproductive organs. But in some of 

 these plants, the seeds also differ in shape and sculpture. 

 These differences have sometimes been attributed to the 

 pressure of the involucra on the florets, or to their 

 mutual pressure, and the shape of the seeds in the 

 ray-florets of some Compositae countenances this idea; 

 but with the Umbelliferae, it is by no means, as Dr. 

 Hooker informs me, the species with the densest heads 

 which most frequently differ in their inner and outer 





