EE VIEWS. 
635 
of scientific annals. Bringing a logical mind to bear on the confused col- 
lection of facts and inferences, he separates the former from the latter — the 
grain from the chaff — and proceeds to add something to our previous know- 
ledge of Nature’s laws. Such men are the real supporters of science, which, 
without them, would dwindle into a contemptible empiricism ; they stand 
out in all ages as the landmarks of philosophy, and are respectively asso- 
ciated with the links which constitute the chain of natural science. We 
have been led to these remarks by an examination of the two works now 
before us ; essays which, notwithstanding their imperfections, tend more to 
advance the philosophy of zoology than a thousand of the ordinary treatises 
which our scientific publishers so lavishly supply us with. The two writers, 
M. De Quatrefages and Dr. Ogilvie, have chosen pretty nearly the same 
subject for investigation — that of the laws regulating the changes which 
animals undergo from the period of ovum to the condition of sexual adult ; 
but the former has been the first in the field, and has confined his attention 
nearly exclusively to animals, while the latter, who has just made his appear- 
ance as a teacher in these departments of knowledge, has extended his inquiries 
to the vegetable kmgdom. There are two very well-marked distinctions 
between the views and generalizations of the two writers. Those of our 
readers who are acquainted with comparative physiology, are aware that the 
phases through which animals pass from the time they leave the egg tiU they 
arrive at maturity, are of a very varied and complex character, and are by 
no means alike in all classes. They are further aware that in some cases the 
intermediate changes occur within the envelopes of the ovum, while in others 
they are capable of being closely examined by the naturalist, smee they 
occur subsequently to the rupture of the shell-bag. To these alterations the 
term devdo^iment has been given when they occur within the ovum, and 
metamorphosis when they take place external to the egg. Such alterations 
are common to all annuals ; but it happens that in certain groups of creatures 
phenomena of apparently quite another kind take place, which, as it were, 
approximate these beings to plants. From the fertilized ovum there springs 
an independent organism, having definite characters, and capable of 
supplying itself with food. This product, though to all appearance a distinct 
and perfect animal, is devoid of a reproductive system, but is capable of 
either increasing its own extent or producing distinct descendants by a 
process of gemmation. Under such conditions it may remain for a period 
of time, longer or shorter, according to circumstances, but eventually it 
develops reproductive organs, which in some cases remain attached, in others 
become free and floating, and by the sexual combination of the elements, 
of these an ovum is produced, and thus the vital circle is completed. 
These curious deviations from the condition of things we meet with in the 
higher annuals, Messrs. Quatrefages and Ogilvie have set themselves to 
account for, and in doing so they have correlated the various phenomena, 
or rather shown us their correlation, in the expression of very simple 
laws. Let us deal first with M. de Quatrefages. The processes of meta- 
morphosis and of alternation of generations which we have described are, 
according to the French savant, but different manifestations of one and 
the same primary phenomenon — development. He commences by showing 
us that development in the embryonic application, and metamorphosis 
