SYSTEMATIC ZOOLOGY—GILL. 469 
different times to various classes. It is noteworthy that in some 
instances the authors of the new genera quite abruptly changed their 
minds regarding the nature of such groups. For example, Lacépéde, 
in 1798, in the closing lecture of his course at the Museum of Natural 
History, recognized only 51 genera of mammals, but a few months 
later (in 1799), in a “ tableau,” admitted and defined 84 genera. 
It seems to be generally supposed that there has been an uninter- 
rupted tendency among zoologists to refinement and increase of 
number of genera to the present time, but such is by no means the 
case. Half acentury ago and more some ornithologists subdivided old 
genera and made new ones to an extent to which none of the present 
time is prepared to go. For example, Charles Bonaparte, Prince of 
Canino, required eleven genera of gulls to include those now congre- 
gated in one. About the same time, some herpetologists were equally 
radical. Leopold J. F. J. Fitzinger, in 1843, distributed species 
which are now combined by all in the genus Anolis among no less 
than fifteen genera. The genus Bufo, as now understood, was split 
by some herpetologists into a dozen or more. These are only samples 
of numberless analogous cases. 
THE OLD AND THE NEW. 
A comparison of systematic zoology at its dawn with that of the 
present time is rather a contrast of different themes. 
The old naturalists believed that all species of animals were created 
as such by a divine fiat; the modern consider that all animals are 
derivatives from former ones and that their differences have been 
acquired during descent and development. : 
The Linneans based their systems on superficial characteristics, and 
the moderns take into consideration the entire animal. 
The early systematists assumed that characters drawn from struc- 
tures or parts most useful to the animals were the best guides to the 
relationship of the animals; the latest ones have learned to distrust 
the evidential value of similarity of structures unaccompanied by 
similarity of all parts. ‘The former were guided mainly by physio- 
logical characters; the latter take morphological ones. 
The Linnzans confined their generalizations to few categories— 
genera, orders, classes; the moderns exhibit the manifold modifica- 
tions and coordinations of all structural parts in many categories— 
genera, subfamilies, families, superfamilies and various higher 
groups. 
The old naturalists believed more or less in the existence of a regu- 
lar chain of beings from high to low; the new ones recognize the 
boundless ramifications of all animal stocks. 
