J. D. Dana on Cephalization. 169 
ter; the second is that from Spiders to Insects (or Octapods to 
Hexapods), the two anterior feet in the former being mouth- 
organs in the latter. One of these cases occurs between the two 
higher divisions of aereal Articulates or Insecteans; and the 
other two between the two higher divisions of the foot-bearing 
aquatic Articulates or Crustaceans. 
legs, but the no less Tetradecapods in type of structure 
and all their relations, These prehensile legs aid in capturing 
food; but they are no more part of the cephalic series than are 
stands alone among Mammals in having the fore-limbs, not only 
prehensile, but out of the inferior series, the posterior pair being 
the sole locomotive organs. 
he question of the exact parallelism of this last of the three 
cases with the preceding two admits of arguments on both sides. 
But whichever way decided, it does not affect in the slightest 
degree our deductions under the principle of cephalization. It 
touches only one single argument on the question whether Man 
Constitutes by himself a separate Order among Mammals, an 
ls, in our view, not seriously. All must admit, whatever his 
views of the question, that this ennobling of the fore-limbs is 
ou mark of that preéminence of cephalization which belongs 
an. 
6. The necessity of an exact balancing of all characteristics 
bearing on grade, in order to arrive at correct results, is too ob- 
Vious for an argument. If the inferior criterion is in any case 
= Our-db 
harrow limits of variation, and a less tendency to run into 
bizarre forms, are set down as generally characteristic of a 
Superior group, and as part of the evidence of the superiority of 
Am. Jour, Sct.—Szconp Serres, Vor. XLI, No. 122—Mance, 1866. ip 
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