454 ORIGIN OF SPECIES 



tance, "like that of all their parts, not only in this, but, as I 

 apprehend, in every natural family, is very unequal, and in 

 some cases seems to be entirely lost." Again, in another 

 work he says, the genera of the Connaracese "differ in having 

 one or more ovaria, in the existence or absence of albumen, 

 in the imbricate or valvular sestivation. Any one of these 

 characters singly is frequently of more than generic impor- 

 tance, though here even vi^hen all taken together they appear 

 insufficient to separate Cnestis from Connarus." To give an 

 example amongst insects : in one great division of the Hy- 

 menoptera, the antennae, as Westwood has remarked, are 

 most constant in structure ; in another division they differ 

 much, and the differences are of quite subordinate value in 

 classification; yet no one will say that the antennae in these 

 two divisions of the same order are of unequal physiological 

 importance. Any number of instances could be given of the 

 varying importance for classification of the same important 

 organ within the same group of beings. 



Again, no one will say that rudimentary or atrophied or- 

 gans are of high physiological or vital importance; yet, un- 

 doubtedly, organs in this condition are often of much value 

 in classification. No one will dispute that the rudimentary 

 teeth in the upper jaws of young ruminants, and certain 

 rudimentary bones of the leg, are highly serviceable in ex- 

 hibiting the close affinity between ruminants and pachyderms. 

 Robert Brown has strongly insisted on the fact that the posi- 

 tion of the rudimentary florets is of the highest importance 

 in the classification of the grasses. 



Numerous instances could be given of characters derived 

 from parts which must be considered of very trifling physio- 

 logical importance, but which are universally admitted as 

 highly serviceable in the definition of whole groups. For in- 

 stance, whether or not there is an open passage from the 

 nostrils to the mouth, the only character, according to Owen, 

 which absolutely distinguishes fishes and reptiles — the inflec- 

 tion of the angle of the lower jaw in Marsupials — the man- 

 ner in which the wings of insects are folded — mere colour in 

 certain Algae — mere pubescence on parts of the flower in 

 grasses — the nature of the dermal covering, as hair or 

 feathers, in the Vertebrata. If the Ornithorhynchus had 



