208 CLASSIFICATION. [Chap. XIV. 



nants, and certain rudimentary bones of the leg, are 

 highly serviceable in exhibiting the close affinity be- 

 tween ruminants and pachyderms. Eobert Brown has 

 strongly insisted on the fact that the position 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 physiological importance, but which are univer- 

 sally admitted as highly serviceable in the . definition of 

 whole groups. For instance, whether or not there is an 

 open passage from the nostrils to the mouth, the only 

 character, according to Owen, which absolutely dis- 

 tinguishes fishes and reptiles — the inflection of the angle 

 of the lower jaw in Marsupials — the manner in which 

 the wings of insects are folded — mere colour in cer- 

 tain 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 been covered with feathers instead of hair, this ex- 

 ternal and trifling character would have been consid- 

 ered by naturalists as an important aid in determin- 

 ing the degree of affinity of this strange creature to 

 birds. 



The importance, for classification, of triffing charac- 

 ters, mainly depends on their being correlated with many 

 other characters of more or less importance. The value 

 indeed of an aggregate of characters is very evident in 

 natural history. Hence, as has often been remarked, a 

 species may depart from its allies in several characters, 

 both of high physiological importance, and of almost 

 universal prevalence, and yet leave us in no doubt where 

 it should be ranked. Hence, also, it has been found 



