oard model or a
child's toy, but a living equilibrium; and every day and every hour,
every living thing is being weighed in the balance and found sufficient
or wanting.

Our little book is the merest beginning in zoology; we have stated one
or two groups of facts and made one or two suggestions. The great
things of the science of Darwin, Huxley, Wallace, and Balfour remain
mainly untold. In the book of nature there are written, for instance, the
triumphs of survival, the tragedy of death and extinction, the
tragi-comedy of degradation and inheritance, the gruesome lesson of
parasitism, and the political satire of colonial organisms. Zoology is,
indeed, a philosophy and a literature to those who can read its
symbols. In the contemplation of beauty of form and of mechanical
beauty, and in the intellectual delight of tracing and elucidating
relationships and criticising appearances, there is also for many a
great reward in zoological study. With an increasing knowledge of the
facts of the form of life, there gradually appears to the student the
realization of an entire unity shaped out by their countless, and often
beautiful, diversity. And at last, in the place of the manifoldness of a
fair or a marine store, the student of science perceives the infinite
variety of one consistent and comprehensive Being-- a realization to
which no other study leads him at present so surely.

To the student who feels inclined to amplify this brief outline of
Vertebrate Anatomy, we may mention the following books:
Wiedersheim's and Parker's Vertebrates, Huxley's Anatomy of the
Vertebrata, Flower's Osteology of the Mammalia, Wallace's
Distribution, Nicholson and Lyddeker's Palaeontology (Volume 2),
the summaries in Rolleston's Forms of Animal Life (where a
bibliography will be found), and Balfour's Embryology. But reading
without practical work is a dull and unprofitable method of study.

_Questions on Embryology_

[All these questions were actually set at London University
Examinations.]
{In Both Editions.}

1. Describe the changes in the egg-cell which precede fertilization;
describe the process of fertilization and the formation of the primary
cell-layers, as exhibited, in three of the animal types known to you.
What is the notochord, and how is it developed in the frog?

2. Describe the early stages in the development of the egg of the fowl
as far as the closure of the neural groove. How do you account for
the primi