BRONN ON PAL.EONTOLOGICAL STATICS. 57 



We thus obtain in round numbers 1,500,000 species of animals, 

 and 500,000 of plants. By introducing more appropriate numbers 

 and exponents, our calculation might perhaps be here and there 

 amended, and thus a more correct result obtained ; meanwhile it is 

 sufficient for us at present to have pointed out the method, accord- 

 ing to which we believe that such an estimate must be made ; it is 

 enough for us to have so far obtained a general result, from which 

 the whole succession of the gradually originating and perishing or- 

 ganisms may be reckoned at two millions ; and it is on the whole 

 indifferent at present, whether this may become, in consequence of 

 amended calculations, 1,000,000 or 3,000,000. On the whole, as 

 was stated, only half so many plants are obtained in proportion to 

 the animals ; but in reality the commencing flora, until the appear- 

 ance of the second half of the Monochlamydese, of the Corolliflorse 

 and the Choristopetalse, the number of which is almost three times 

 as great as that of the lower plants, was much more uniform than 

 the fauna, in which, indeed, the more perfect and some other classes 

 in like manner also first appear along with the more perfect classes 

 of plants ; but these perfect classes of animals make (not three, but) 

 only -^ the number of the imperfect classes. 



Of the 2,000,000 species of organisms thus estimated as once ex- 

 isting, probably not -^ were adapted to leave their remains imbedded 

 in a recognizable condition in the strata ; or chance {Zufall) at least 

 has not sufficiently favoured -^-^ of the species for this purpose ; and 

 of the remaining 200,000 species which we might find in the earth's 

 crust, chance will again prevent a large portion from ever coming to 

 our knowledge. 



Returning to the facts presented to us by our tables, we find that 

 the species are most unequally distributed in the formations and 

 periods : — 



V. or I. II. III. IV*. V. 



623 = 0-49 : 005 : O'll : 0-04 : O'Sl 



13,384 = 0-16 : 04 : 0-13 : 0-18: 0-48 



14,007 = 0-18 : 0-04 ; 0-14 : 0-17 ; 0-47 



These inequalities are (independent of the accidental coincidence 

 of our researches with richer or poorer fossil-localities) partly a con- 

 sequence of the unequal preserving-powers of the kind of rock-mass 

 composing each formation either generally or for certain classes and 

 organisms in especial (the coal formation for plants), partly of the 

 wider geographical development of the species and the unequal dura- 

 tion of the periods, which, however, it would be difficult to find a 

 means of measuring, and finally, partly of the unequal richness of the 

 successive formations, which we indeed express in numbers, but still 

 are, from not knowing the value of the two previous influences, inca- 

 pable of so measuring as to be able to say, which period estimated 

 for times of equal length was the richer. We were for some moments 

 disposed to estimate equal duration of the periods from equality in 

 the numbers or quota of fossil species which passed from the first 



* In the original the numbers in this column are, 0*040, 001 8, 0*017, but 

 evidently from a misprint. — J. N. 



Periods. 



I. 



II. 



III. 



IV. 



Plants : species . . . 



. 1017 



98 



241 



84 



Animals : species . . 



. 4445 



1091 



3892 



4816 



Both : species . . . 



. 5462 



1189 



4133 



4900 



