Ix THE DEBT OF SCIENCE TO DARWIN 47] 
be due to a few simple instincts which necessarily lead to the 
exact hexagonal cell with the base formed of three triangular 
plates inclined at definite angles, on which so much mathema- 
tical learning and misplaced admiration have been expended ; 
and this explanation is no theory, but is the direct outcome 
of experiments on the bees at work, as original as they were 
ingenious and convincing. 
The Descent of Man and Later Works 
We must, however, pass on to the great and important work, 
The Descent of Man and on Selection in Relation to Sex, which 
abounds in strange facts and suggestive explanations; and 
for the reader who wishes to understand the character and 
bearing of Darwin’s teachings, this book is the fitting supple- 
ment to the Origin of Species and the Domesticated Animals and 
Plants. To give any adequate account of this most remark- 
able book and the controversies to which it has given rise, 
would require an article to itself. We refer to it here in 
order to point out what is not generally known, that its 
publication was entirely out of its due course, and was not 
anticipated by its author three years before. In the intro- 
duction to Domesticated Animals (published in 1868), after 
explaining the scope of that work, he tells us that in a 
second work he shall treat of “Variation Under Nature,” 
giving copious facts on variation, local and general, on races, 
sub-species and species, on geometrical increase, on the struggle 
for existence, with the results of experiments showing that 
diversity of forms enables more life to be supported on a 
given area, while the extermination of less improved forms, 
the formation of genera and families, and the process of 
natural selection, will be fully discussed. This work would 
have given all the facts on which chapters ii. to v. of the 
Origin of Species were founded. Ina third work he proposed 
to show, in detail, how many classes of facts natural selection 
explains, such as geological succession, geographical distribu- 
tion, embryology, affinities, classification, rudimentary organs, 
etc, etc., thus giving the facts and reasonings in full on 
which the latter part of the Origin of Species was founded. 
Unfortunately, neither of these works has appeared, and thus 
the symmetry and completeness of the body of facts which 
