148 
Reviews. 
that we find a logically satisfactory method of attack. It should 
never be forgotten that though an organism is a machine, it is not 
a brand-new one constructed to fulfil its present functions, but has 
been built up and modified step by step according to the slowly 
changing needs of its ancestors. 
Ever since the original publication of Haberlandt’s work, to 
which his own research has in almost every part greatly contri¬ 
buted, his book has been the standard account of physiological 
anatomy. The logical division of the subject, the lucid style, and 
the clear distinction of well ascertained fact from speculative 
suggestion have combined to render it a model text-book. The 
second edition, published in 1896, was greatly enlarged and brought 
up to date, while the present (third) edition has undergone the same 
process, though, appearing after a shorter interval it has not been 
enlarged to the same extent. The book now consists of over 600 
pages with 264 illustrations. The old division into sections dealing 
with the different physiological tissue-systems is retained, the prin¬ 
cipal change from the second edition being the addition of three 
new sections, on the apparatus of movement, on sense-organs, and 
on mechanisms for the conduction of stimuli, respectively. 
The second of these sections begins by shewing that in the 
in the course of progressive division of physiological labour, special 
sensitiveness, at first diffused over the whole protoplasm of an 
organism, becomes gradually restricted to separate tissues, though 
these may be primarily adapted to some other function. As an 
example we may take the epidermis, which in many tendrils, for 
instance, is the tissue sensitive to contact-stimuli, while in leaves it 
is very probable that this layer, though primarily a protective and 
water-storing tissue, is also the light-perceiving organ. 
In the highest grade of adaptation, the perceptive power is 
localised in a tissue whose sole function it is. In such cases, of 
course, the anatomical structure of the organ is clearly adapted to 
its function, and the term sense-organ is properly applied. As Noll 
pointed out, it is to the fixed ectoplasm of the cell in all cases that 
we must look for the reception of definite external stimuli, whether 
in non-specialised or in specialised sense-cells. 
The sense-organs are treated under “ Sense organs for 
mechanical stimuli ”—tactile pits, papillae, hairs and bristles, “sense 
organs for geotropic stimuli,” and “ sense organs for light-stimuli.” 
There is an excellent account given of the “statolith ” theory of the 
mechanism for the perception of geotropic stimuli, but there appears 
to be no reference to the “radial pressure” theory, and in the present 
