the "Christian Examiner," Boston, for May; 3. M. Pictet's article in
the "Bibliothèque Universelle," which we have already made
considerable use of, which seems throughout most able and correct, and
which in tone and fairness is admirably in contrast with, 4. the
article in the "Edinburgh Review" for May, attributed--although
against a large amount of internal presumptive evidence--to the most
distinguished British comparative anatomist; 5. an article in the
"North British Review" for May; 6. finally, Professor Agassiz has
afforded an early opportunity to peruse the criticisms he makes in the
forthcoming third volume of his great work by a publication of them in
advance in the "American Journal of Science" for July.

In our survey of the lively discussion which has been raised, it
matters little how our own particular opinions may incline. But we may
confess to an impression, thus far, that the doctrine of the permanent
and complete immutability of species has not been established, and may
fairly be doubted. We believe that species vary, and that "Natural
Selection" works; but we suspect that its operation, like every
analogous natural operation, may be limited by something else. Just as
every species by its natural rate of reproduction would soon fill any
country it could live in, but does not, being checked by some other
species or some other condition,--so it may be surmised that Variation
and Natural Selection have their Struggle and consequent Check, or are
limited by something inherent in the constitution of organic beings.
We are disposed to rank the derivative hypothesis in its fulness with
the nebular hypothesis, and to regard both as allowable, as not
unlikely to prove tenable in spite of some strong objections, but as
not therefore demonstrably true. Those, if any there be, who regard
the derivative hypothesis as satisfactorily proved must have loose
notions as to what proof is. Those who imagine it can be easily