184 LAMARCK, HIS LIFE AND WORK 
ness, and better satisfies the views now prevailing, 
than that of any other author. 
His definition of a species is as follows: 
“Every collection of similar individuals, perpetu- 
ated by generation in the same condition, so long 
as the circumstances of their situation do not change 
enough to produce variations in their habits, charac- 
ter, and form.”’ 
Lamarck’s rare skill, thoroughness, and acuteness 
as an observer, combined with great breadth of view, 
were also supplemented by the advantages arising 
from residence in Paris, and his connection with 
the Museum of Natural History. Paris was in the 
opening years of the nineteenth century the chief 
centre of biological science. France having con- 
valesced from the intestinal disorders of the Revolu- 
tion, and, as the result of her foreign wars, adding to 
her territory and power, had begun with the strength 
of a young giant to send out those splendid exploring 
expeditions which gathered in collections in natural 
history from all parts of the known or accessible 
world, and poured them, as it were, into the laps of 
the professors of the Jardin des Plantes. The shelves 
and cases of the galleries fairly groaned with the 
weight of the zoélogical riches which crowded them. 
From the year 1800 to 1832 the French government 
showed the greatest activity in sending out explor- 
ing expeditions to Egypt, Africa, and the tropics.* 
* During the same period (1803-1829) Russia sent out expeditions 
to the North and Northeast, accompanied by the zodlogists Tilesius, 
Langsdorff, Chamisso, Eschscholtz, and Brandt, all of them of Ger- 
