64 HUXLEY, ON CLASSIFICATION. 
tend to follow Professor Huxley into those details which lead 
him to differ with Professor Owen with regard to the theo- 
retical structure of the vertebrate skull. We can only say, 
with regard to this second part of his work, that it will 
afford to all students of comparative anatomy, an example of 
how great is the power of analysis demanded of, and how wide 
are the inquiries of, the philosophical anatomist. It is only in 
a very subsidiary way that the minute inquiries of the micro- 
scopist can assist the anatomical philosopher in arriving at 
the general laws which regulate the morphology of the higher 
classes of the animal kingdom. 
It is in the lower forms of animal life that the zoologist 
must’ have recourse to the microscope. Whole families and 
tribes of every division of Invertebrate animals can alone be 
detected by the aid of the microscope, and it is by its aid 
alone that the comparative anatomist and zoologist have 
been enabled to group the various species into something 
like harmonious relationship. It would be almost impossible 
for us to criticise the various positions taken by Professor 
Huxley with regard to the classification of the lower animals. . 
He has recast the groups formerly known so well as the 
Radiata, of Cuvier, and which embraced so large a field 
of inquiries open to the microscopist, and we take advan- 
tage of the permission of the publishers to reproduce the first 
lecture of this series entire. 
THE GREGARINIDA, RHIZOPODA, SPONGIDA, AND 
INFUSORIA. 
By the classification of any series of objects, is meant the actual, 
or ideal, arrangement together of those which are like and the 
separation of those which are unlike; the purpose of this arrange- 
ment being to facilitate the operations of the mind in clearly 
conceiving and retaining in the memory, the characters of the 
objects in question. 
Thus, there may be as many classifications of any series of natural, 
or of other, bodies, as they have properties or relations to one 
another, or to other things; or, again, as there are modes in which 
they may be regarded by the mind: so that, with respect to such 
classification as we are here concerned with, it might be more proper 
