IN NATURAL HISTORY. 7 
in this classification of Linnzus; his class of 
Worms, also, was most heterogeneous, for he 
included among them Shell-Fishes, Slugs, Star- 
Wishes, Sea-Urchins, Corals, and other animals 
that bear no relation whatever to the class of 
Worms as now defined. 
But whatever its defects, the classification of 
Linnzus was the first attempt at grouping ani- 
mals together according to certain common struc: 
tural characters. His followers and pupils en- 
gaged at once in a scrutiny of the differences 
and similarities among animals, which soon led 
to a great increase in the number of classes; in- 
stead of six, there were presently nine, twelve, 
and more. But till Cuvier’s time there was no 
great principle of classification. Facts were ac- 
cumulated and more or less systematized, but 
they were not yet arranged according to law; 
the principle was still wanting by which to gen- 
eralize them and give meaning and vitality to the 
whole. It was Cuvier who found the key. He 
himself tells us how he first began, in his investi- 
gations upon the internal organization of animals, 
to use his dissections with reference to finding the © 
true relations between animals, and how ever 
after his knowledge of anatomy assisted him in 
his classifications, while his classifications threw 
new light again on his anatnmical investigations, 
--each science thus helping to fertilize the other. 
