84 
POPULAR SCIENCE REVIEW. 
li&s long been much wanted, — a tborouglily good and trustworthy English 
treatise on the morphology of the Invertebrates. And a pretty close inspec- 
tion of it, whilst revealing one or two points to which we might, perhaps 
with some ground, demur, shows, nevertheless, that, so far as can be expected 
from a manual dealing with so vast a field, these anticipations are fulfilled. 
Throughout the book the structure and development of the animals forming 
the great natural groups of Invertebrata are admirably described, and many 
particulars as to their relations to the world outside of them are given. 
In carrying out this plan the author has not attempted to give any pro- 
minence to the question of classification, his object being, as he says in his 
preface, to give clear ideas of the morphology of the great natural “ orders ” 
(classes of most zoologists), leaving the question of larger natural divisions 
to some extent on one side ; and in this way, while the different well-known 
groups are brought together under definite sections, certain others, of doubt- 
ful affinities, are treated of in a final chapter, together with one or two 
which have been established since the earlier portion of the work was 
printed. But this apparent disregard of classification is due to no depre- 
ciation of its importance, but rather to Professor Huxley’s feeling, that at 
the present moment the science of zoology is still in a somewhat uncertain 
state, the old hard and fast lines of system having been considerably 
broken in upon, whilst no new views have been put forward with sufficient 
force to take their place. According to the author (and we think this 
expression of opinion may perhaps have a beneficial influence on the minds 
of some of our younger zoologists), classification is the “ superstructure 
and outcome ” of morphology ; or, in other words, the best classification is, 
as it was always considered by the older zoologists, the best exposition of the 
sum of our knowledge of the organisms under consideration. 
One is the better pleased to find a naturalist like Professor Huxley 
taking this view of the present state of Zoology, because he is, as his new 
work sufficiently shows, deeply imbued with the views of development 
maintained by Hackel ; and both that distinguished professor and many of 
his followers adopt a rather strongly dogmatic tone in expressing their 
opinions on systematic points. We are all familiar with the beautiful 
genealogical trees which have lately been so often put forward. Professor 
Huxley treats us to nothing of the kind ; but he speaks of phylogeny as 
u a special branch of biological investigation f and adds : “ In practice, the 
reconstruction of the pedigree of a group from the developmental history 
of its existing members is fraught with difficulties. It is highly probable 
that the series of developmental stages of the individual organism never 
presents more than an abbreviated and condensed summary of ancestral 
conditions, while this summary is often strangely modified by variation 
and adaptation to conditions ; and it must be confessed that, in most cases, 
we can do little better than guess what is the genuine recapitulation of 
ancestral forms, and what is the effect of comparatively late adaptation.” 
He hopes that by phylogenetic investigations, founded on the study of 
ontogenetic development and of fossil organisms combined, “ a perfectly 
safe foundation for the doctrine of Evolution ” may be arrived at. 
With regard to the fundamentals of the doctrine of Evolution, Professor 
Huxley is equally candid. He says : “ Three views may be taken of the 
causes of variation : 
