144 LAWS OF VAKIATION. Chap. V. 



the petals of the corolla into a tube. Hard parts seem 

 to affect the form of adjoining soft parts ; it is believed 

 by some authors that the diversity in the shape of the 

 pelvis in birds causes the remarkable diversity in the 

 shape of their kidneys. Others believe that the shape 

 of the pelvis in the human mother influences by pres- 

 sure the shape of the head of the child. In snakes, 

 according to Schlegel, the shape of the body and the 

 manner of swallowing determine the position of several 

 of the most important viscera. 



The nature of the bond of correlation is very fre- 

 quently quite obscure. M. Is. Geoffroy St. Hilaire has 

 forcibly remarked, that certain malconformations very 

 frequently, and that others rarely coexist, without our 

 being able to assign any reason. What can be more 

 singular than the relation between blue eyes and deaf- 

 ness in cats, and the tortoise-shell colour with the female 

 sex ; the feathered feet and skin between the outer toes 

 in pigeous, and the presence of more or less down on the 

 young birds when first hatched, with the future colour of 

 their plumage ; or, again, the relation between the hair 

 and teeth in the naked Turkish dog, though here pro- 

 bably homology comes into play ? With respect to this 

 latter case of correlation, I think it can hardly be acci- 

 dental, that if we pick out the two orders of mammalia 

 which are most abnormal in their dermal covering, viz. 

 Cetacea (whales) and Edentata (armadilloes, scaly ant- 

 eaters, &c), that these are likewise the most abnormal 

 in their teeth. 



I know of no case better adapted to show the im- 

 portance of the laws of correlation in modifying im- 

 portant structures, independently of utility and, there- 

 fore, of natural selection, than that of the difference 

 between the outer and inner flowers in some Compo- 

 sitous and Umbelliferous plants. Every one knows the 



