49 
in the Distribution of Vegetable Forms. 
proportion of 1 : 4,S. Such an agreement between two opposite 
zones is abundantly striking. The Birds, and especially the 
Reptiles, increase towards the equatorial zone in a much more 
considerable degree than the Mammalia. According to the dis- 
coveries of M. Cuvier regarding fossil bones, we maybe induced 
to believe, that these proportions have not been the same in all 
ages, and that, amid the ancient catastrophes of our planet, a 
much greater numb^ of Mammalia has been lost than of Birds. 
M. Latreille, in an excellent memoir on the Geographical Dis- 
tribution of Insects, has not compared the number of articulated 
animals with the number of plants, and with that of the diffe- 
rent classes of vertebral animals which inhabit the same cli- 
mates ; but he has exhibited, in an interesting ^^manner, a view 
of the increase or diminution of the particular groups of insects, 
in advancing from the pole towards the equator. I pass over 
in silence the laborious researches of M. Illiger on the Geo- 
graphy of Birds The author has discussed the habitation of 
upwards of S800 species ; but he has contented himself with 
viewing them according to their distribution among the five di- 
visions of the world, — a method by no means philosophical, and 
altogether improper for investigating the influence of climate 
over the development of organized beings. All the continents, 
with the exception of Europe, extend from the temperate to the 
equatorial zone : the laws of l^ature cannot, therefore, manifest 
themselves, when we group the phenomena according to divi- 
sions which are arbitrary, and which depend, so to speak, sim^ 
ply upon the difference of meridians. It is not my intention to 
push to a greater extent these considerations regarding the nu- 
merical proportions of animals of different classes. I am satis^ 
fied with having called the attention of the learned to a branch 
of natural philosophy which has appeared to me very worthy 
of investigation. We conceive how, in a given space of coun- 
try, the individuals belonging to different tribes of plants and 
of animals may be numerically limited.^ — how, after an obsti- 
nate struggle, and long wavering, a state of equilibrium is esta- 
* Memoirs of the Academy of Berlin for the years 1812 and 1813, p. 221,-^ 
237. 
VOL. VII. NO. 13. JULY 1822. 
D 
