238 FISSIROSTRAL SUBORDER OF 



bers, nor specially to the view of the subject which I am myself 

 reconimeadiDg. We do not prescribe either through how many 

 steps the subdivision of secondary types needs to be carried, nor 

 how many grades of development a type shall admit. We lay down 

 a general law as founded on observation that under each more gene- 

 ^ral plan of structure the secondary divisions are five, each indicating 

 development in a particular direction, or according to a particular 

 idea, and therefore each having a certain more or less distinctly per- 

 ceived analogy with the corresponding division under a different type* 

 Such a law indicates a regular natural relation among the members 

 of the animal kingdom, and a definite plan in the mode of adapting 

 different creatures to their different positions ; but it places no liir.ifc 

 that we can perceive to the extent of creation, and it only opens to 

 us some imperfect view of the means by which the union of order 

 ■with variety is accomplished. Mr. Wallace takes the example of a 

 particular family (the Parrots) to show that our system exactly fixes 

 how many forms of Parrots can possibly exist in Nature, so that our 

 work is merely to find them and assign to them their places ; that we 

 are masters of the limits of nature, and anything out of our scheme 

 is inconceivable. Suppose, then, that we have a definite idea of what 

 constitutes a member of the family of Psittacidse. If our views be 

 correct, the members of this family will readily fall into five sub- 

 families, each distinctly exhibiting a certain tendency. If those 

 demand further subdivision, the same tendencies will bo again mani- 

 fested within a more limited field oi variation, and this will go on to 

 any required extent, the groups next to the species being genera, or 

 possibly sub-genera, but the number of the intermediate divisions 

 depending on the extent and variability of the family. Would a 

 botanist insist on as many intermediate steps in classification in the 

 order Violacese as in Pabaceee ? We have here, then, ample means 

 of disposing of numerous species, provided they all exhibit the kind 

 of relations implied in the sub-families ; but suppose even that our 

 researches should bring to our knowledge some birds manifestly not 

 conforming to any of the five sub -families, our law would lead us to 

 expect that they would each still imitate one of the sub-families iu 

 its tendency of development, but must belong to a higher or lower 

 grade of development ; in either case we extend our actual know- 

 ledge of birds, without placing any limit to the variety of creation, 

 yet with a constant sense of the relation of the new object to those 

 previously known, and to a plan which pervades living nature. If 



