of the Dichotomous System. 205 



to its facility, on which head I can only say that when this 

 worthy has produced to the world a natural group differently 

 divided into five circles, each two connected by parallel ana- 

 logies, then I will believe him. To do it once, the once of 

 nature is abundantly difficult, and the proof is the slowness 

 with which we are evolving the system. 



Only two objections of Dr. Fleming's remain to be consi- 

 dered. The first of these is, that " one set of organs are em- 

 ployed to establish a connection here, and another to establish 

 a connection there." And why not? The white man and 

 the negro are distinguished by their feet ; while the Asiatic 

 and African elephants are known from other animals by their 

 trunk. I admit therefore the fact, and yet our system when 

 completed will express the variation of all organs. Will it be 

 believed that I am perhaps one of the first after Lamarck who 

 attempted to prevent the selecting such systems of organs at 

 hazard, and perhaps the very first who prescribed the fol- 

 lowing rule for their choice ? " Like every other solitary 

 character that can possibly be adopted for the groundwork 

 of a zoological system, the mode of generation ought to rise 

 in importance only in inverse proportion to its degree of va- 

 riation. In a group of animals for instance, where it varies 

 according to the species, it is manifestly of less importance as 

 affording natural characters, than among those groups where 

 it remains less subject to variation." These words prove that 

 although we neglect no characters, yet we have a rule for 

 deciding upon their respective values. 



The other objection is stated as follows : " The same means 

 which the quinarians employ to divide a group when a fifth is 

 wanting might enable them to subdivide others." Now the 

 same means will not enable them to subdivide others; for they 

 have remarked in nature that every natural group returns into 

 itself, in other words is a circle, and no group presents to their 

 view more than five such groups of equal degree returning into 

 themselves. Again the Doctor destroys himself by an exam- 

 ple. "What," says he, "but the most obvious prejudices could 

 induce Mr. MacLeay to divide Insecta into Mandibulata and 

 Haicstellata, and leave entire the Arachnida??" He affords the 

 answer himself, but I scorn to take advantage of his ignorance. 

 He means Arachnida *, and I will now answer his question. 

 Mandibulata and Haustellata do not present one circle, but 



* Let Dr. Fleming visit the Collections of the Metropolis; there he will see 

 a variety of forms of Arachnida ; or still better, for Arachnida are not easily 

 preserved, let him visit the Torrid Zone, the metropolis of Arachnida, and 

 he will see a continuity of forms as remarkable as in Mandibulata or Haus- 

 tellata. It is only a week since I discovered a spider with only two eyes, 

 and every day produces something new in this class. 



two, 



