REVIEW. ', FS 
matters as the meaning of the terms “individual,” “organ,” and 
* stock,’ the symmetry of animals, cells and cell-tissues, differen- 
tiation, the correlation and connection of organs, the structure 
and function of the ccmpound organs, intelligence and instinct, 
development, alternation of generations, polymorphism and _heter- 
ogamy. The fourth chapter is devoted to an interesting historical 
review of the progress of Zoology from Aristotle downwards, and ends 
by giving brief definitions of the nine “Types” or primary subdivi- 
sions of the Animal Kingdom adopted by the author. The fifth 
chapter is headed “ Meaning of the System;” it describes what is 
meant by such terms as “Species” and ‘ Variety,’ and gives an 
excellent account of the Theory of Descent and of the evidence in 
favour of it. Under the latter head is a good summary of the subject 
of Geographical Distribution, as well as a bricf account of the 
structure and formation of the earth’s crust; and the chapter ends 
with an account of the relations of fossil to living species. 
Prof. Claus’s views on the fundamental problems of Zoology are 
thoroughly sound and free from dogmatism. For instance, on the 
question of so-called spontaneous generation he says truly enough 
that the doctrine “appears to be a necessary postulate in order to 
explain the first appearance of organisms,” but continues further on 
“we might look upon the first appearance of life as essentially only 
the solution of a difficult mechanical problem, were we not obliged to 
conclude that there is present even in the simplest and most primitive 
organisms the germs of sensation and consciousness, attributes which 
we cannot regard as simply the results of the movement of matter.” 
The author is opposed to the formation of a.‘ Regnum Protis- 
‘ticum ” (Haeckel) for the reception of the simplest organisms, and 
considers that such a course “is neither scientifically justified, nor 
from practical considerations desirable.” Most teachers will agree 
with the latter part of this dictum; the separation of the lowest 
animals and plants as Protista would be an undoubted practical 
inconvenience, but one finds it difficult to admit that it is anything 
but thoroughly philosophical to give expression in our classifications 
to the undoubted fact that the vegetable and animal kingdoms diverge 
from a common assemblage of undifferentiated forms. In fact it 
may be said that the separation of Protista from animals and plants 
is neither more nor less “scientifically justified” than the separation 
of animals and plants from one another. 
As to the nature of the individual, Claus holds the same view as 
Haeckel, Lankester, and Balfour, that is, he considers that “ com- 
pound animals” or “animal stocks” are “morphologically aggrega- 
tions of individuals which behave physiologically as organs.” This 
view is totally opposed to that of Huxley who considers the individual 
to be the total product of the development of a single impregnated 
ege: it renders the logical definition of “individual” practically 
impossible, and is in fact, tantamount to holding with Mr. Geddes, 
that there is no such thing as absolute individuality. 
In the section dealing with Organic Evolution there are some 
passages which should be laid to heart by every one who has been 
infected—and who has not?—with the dogmatism of Haeckel and 
others of the “ cock-sure ” school of Biologists. For instance—“ It is 
clearly a great exaggeration when enthusiastic. supporters of the 
Darwinian theory say that it ranks as equal to the gravitation theory 
