PREFATORY ADDRESS. 
iv 
merit ; but, if we desire to obtain the higher intellectual developments of a well-regulated 
mind — such as the faculty of a retentive memory, a power of detecting the most subtile 
distinctions between one thing and another, and a thorough comprehension of our social 
position — we must look to the culture of our mental processes. The absence of a retentive 
memory is by no means indicative of original stupidity, want of industry, or lack of talent ; 
yet, those who would become masters of this valuable product of mental discipline, can only 
do so by pursuing some subject, the study of which involves a methodized and continuous 
process of abstract reasoning. Confusion and obliviousness are often the result of indiscrimi- 
nate observation, and the highest degree of cerebral activity will fail to recall facts once 
familiarly known, unless the storehouse of the mind has been filled in a gradual and 
tentative manner. 
In early times, the cultivators of Natural History science confined themselves, for the 
most part, to the mere collection of cabinet specimens, whose individual worth was estimated 
by comparative beauty or singularity of form, whilst the more important facts and pheno- 
mena respecting the relation of these animal, vegetable, and mineral bodies, the one to the 
other, were entirely overlooked. As years rolled on, the united energies of many hard- 
working naturalists projected only a few thin rays of light upon the chaos of accumulated 
facts, until at length the genius of Linnasus and Jussieu, of Goethe and Oken, of Hunter 
and Ray, of Cuvier and Lamarck, eclipsed these feeble scintillations by the effulgent bright- 
ness of their giant intellects. In later times, the Natural History sciences owe their rapid 
progress rather to the combined investigations of the many, than to the isolated efforts of 
the few, 80 that all the various departments of Zoology, Botany, and Geology acknowledge 
one or more presiding heads to whom they are severally indebted foi: their advancement — 
such as Westwood in Entomology; Audubon and Gould in Ornithology; Bell and Dana 
in Crustaceology ; Von Siebold in Helminthology; Busk and Allman in Zoophy tology , 
and so forth. As a whole, however. Biological science has been impelled forward most 
significantly by those, who, in addition to their promotion of specialities, have given more 
or less comprehensive generalizations, as exemplified in the writings of J. Muller, Agassiz, 
Owen, Huxley, E. Forbes, J. D. Hooker, Bindley, Darwin and others. It is extremely 
difficult to estimate the combined value of independent and widely different researches, such, 
for example, as those of Kblliker and Leydig in Histology; of Van der Hoeven and J. E. 
Gray in Zoology ; of Hermann Von Meyer and Leidy in Paleontology ; of Brongniart and 
Bowerbank in Fossil Botany, &c. ; and yet, if one mind could be found capable of retaining 
within its grasp the multitudinous facts which these and similar investigations have 
separately unfolded, we cannot doubt that a flood of light would be thrown upon their 
intermutual relations and special dependence on the objects by winch they are surrounded. 
Notwithstanding this drawback, however, we are bold enough to state that men of science 
have now fairly realized the fundamental unity of plan pervading all-created nature through- 
out time and space. Those who look upon Botany, Zoology, and Geology as so many 
distinct sciences, should bear in mind that the laws regulating the facts, which these various 
branches of study have generally brought to light, exhibit but one grand scheme of contriv- 
