58 SAMUELSON, ON HUMBLE CREATURES. 
selected as the subject of his labours such common objects as 
the earthworm and the house-fly, whose extreme vulgarity 
would lead many to deem that they were beneath the notice 
of the scientific student. It is, however, a very important 
principle to bear in mind, that in most cases the rarity of 
any object, or the difficulty of obtaining it, in no way adds 
to its value as a subject for the exercise of observation and 
research. In a scientific point of view, it is quite true that 
the commonest objects are, in most respects, as interesting 
as the rarest. The laws of biology, or the physiological and 
structural relations of living beings, may be as well studied 
and as profitably investigated in the commonest as in the 
rarest creatures. As Mr. Samuelson’s book will serve to 
show, no one need go far from his threshold, nor spend 
much time and money in the search after objects upon which 
to spend his leisure hours of observation. It may be 
remarked also, as in the case more particularly of the earth- 
worm, that it not unfrequently happens that the commonest 
and apparently meanest objects are those about which least 
is really known. ‘The structure of the common worm, it is 
needless to say, is as perfect and beautiful as that of the 
highest animal; but common as it is, and numerous as have 
been the observations made with respect to it, many points 
in its structure, physiology, and habits, of the utmost 
importance, yet remain to be made out, a knowledge of 
which would nevertheless tend to throw very considerable 
light upon similar points in a great number of the annulose 
class, which are far less easily procured. Nothing, for 
instance, is yet really known with respect to the mode or the 
situation in which, or the period when, the ova of the earth- 
worm are impregnated; nor, which is perhaps still more 
strange, do we know with certainty how the ova are expelled 
from the parent. The most recent researches on these 
points by D‘Udekem and Hering have, it is true, indicated 
the true situation and some of the relations of the ovaries, 
and the complicated structure of the male reproductive 
organs; but further than this inquiry has not yet gone. 
We cite this particular instance merely to confirm the pro- 
position that, even in the commonest objects, much may yet 
be left for even the best informed inquirer to complete, and 
that they will at any rate always afford to the beginner 
abundant materials for his research. 
With respect to the mode in which Mr. Samuelson has 
executed his task, we need only remark that, although he 
has very properly expressed himself in an easy and popular 
manner, his treatment of the subject is by no means super- 
