based on the Princi]ple of Cephalization. 101 



outweighs his. The Megathere, although much more powerful 

 than a Rodent, has not, on this account, as his structure and 

 habits show, any claims to a place above the lowest of Micros- 

 thenes. 



The terms Megastlienes and Microsthenes are not to be under- 

 stood as signifying large Mammals and small Mammals, but 

 Mammals of strong life-system and weak life-system. Comparing 

 the typical species of Megastlienes* with those of Microsthenes, 

 there is some correspondence between average size of structure 

 and strength of life- system. But a comparison of the typical of 

 the former with the degradational of the latter leads to very false 

 results. 



An approximation to the right ratio is obtained from a com- 

 parison of the degradational species of each ; but this is of no im- 

 portance in its bearing on the question, since vegetative growth is 

 apt to give the greatest proportional enlargement to the lowest 

 species. 



These facts teach that relative size of body, or of brain, is no 

 necessary test of relative rank. The ratio, in hulk, of 1 : 3 between 

 the brain of an average Man and that of a gorilla tells nothing 

 of the actual difference of life-system, or of brain-power. The 

 relative lineal dimensions of Microsthenes and Megasthenes has 

 been estimated at 1 : 4, which gives, for the relative hulk, 1 : 64. 

 If this be the typical ratio between the life systems of the highest 

 Microsthenes and highest Megasthenes, surely that between the 

 hio:hest Meo-asthenes and normal man — he constitutino- a distinct 

 order — must be at least as great. 



The same ratio of 1 : 4, as shown by the writer, is that for the 

 mean size, lineally, of Tetradecapods and Decapods, under Crus- 

 taceans. In two cases, then, consecutive orders differ by a like 

 ratio, or approximately so, in dimensions. As has been remarked, 

 deductions from mere size may be very erroneous ; yet there is no 

 reason, in either of the above cases, to suppose the ratio of life- 

 systems less than that thus indicated. May not, therefore, some 

 similar ratio exist between other analogous consecutive orders, 

 where size does not manifest it, — as, for example, between Spiders 

 and Insects ? And is not the ratio a much greater one between 

 the highest of Insecteans and highest of Crustaceans, since these 

 subdivisions of Articulates are not orders but classes ? Impor- 

 tant results may How from following out the idea here touched 

 upon. 



* These orders of Mammals, make parallel series — the Chiropters or Bats 

 of tlie Microsthenes representing the Quadrumanes of the Megasthenes, the 

 Insectivores representing the Carnivores, the Eodents the Herbivores, and 

 the Edentates the Mutilates. 



