JanvaRY. 29, 1914] 
NATURE 
605 
flag, unless it aids him in action that requires 
thought. It must, in fact, be “‘ thought-compell- 
ing with a view to action, mental or physical, or 
both.” Gardening is held to provide the new 
stimulus that is necessary. In gardening, how- 
ever, the study of nature must still be continued. 
A course of practical work is therefore described, 
in which the principles underlying each operation 
are sought for, these being often made the subject 
of experiment. The only danger is that in follow- 
ing the course the teacher’s zeal for experiment 
may outrun the pupil's desire for information. 
Probabiy Mr. Logan, whese reputation as a leader 
in the school gardening movement in the north 
of Scotland has long beén established, would be 
the first to warn teachers against making this 
mistake. 
The practical work of the school garden is well 
described. The chapters on the cultivation of the 
plots are followed by chapters on propagation, 
manuring, soil organisms, fruit culture, and plant 
diseases. Each is full of useful suggestions for 
the teacher. The workshop is made the adjunct 
of the garden, and a number of garden appliances 
are described which can be made in the woodwork 
class. This, together with “correlated exercises ”’ 
in geography and arithmetic, help to show how to 
link up gardening with the rest of the school 
curriculum. 
The book can be commended to teachers of rural 
schools, both elementary and secondary. 
(2) In the opinion of the author, school garden- 
ing is more often carried on as if the mere acquisi- 
tion of knowledge were the object, than as a 
process of discovery, which, as in other forms of 
handwork, leads to _ self-dependence gained 
through experience of both failure and success. 
His book therefore contains less horticulture than 
in previously published manuals, but more educa- 
tional suggestion, and this is put so forcibly 
that every school teacher of gardening would do 
well to read it. 
A vivid idea is given of the educational possi- 
bilities of gardening. Though Mr. Brewer depre- 
cates any forced correlation, his pupils’ know- 
ledge of even the primary subjects would develop 
by working in the manner he suggests. More- 
over, the natural history of the garden has to be 
studied, garden requisites have to be made in the 
workshop, and simple, though exact, experiments 
of a kind likely to suggest themselves to the 
pupils have to be made. The practical examples 
given are of exactly the right type to capture the 
interest of boys of eleven to fourteen. In fact, 
working on such lines they would want no teach- 
ing; they would teach themselves. 
NO. 2309, VOL. 92| 
OUR BOOKSHELF. 
Vergleichende Physiologie und Morphologie der 
Spinnentiere unter besonderer Berucksichtig- 
ung der Lebensweise. By Prof. F. Dahl. 
Erster Teil: Die’ Beziehungen des Korperbaues 
und der Farben zur Umgebung. Pp. vi+113. 
(Jena: Gustav Fischer, 1913.) Price 3.75 
marks. 
Tuts book is the first instalment of a work 
dealing exclusively with one class of Arthro- 
pods, to wit the Arachnids. It is an account of 
the external form and coloration of these animals 
in relation to their surrounding's, and the author’s 
point of view set forth in the preface will com- 
mend itself to many zoologists, especially those, 
who have to teach young’ students. 
The first thirty pages contain a systematic 
review of the group down to the families thereof, 
and the illustrative woodcuts are excellent. After 
proclaiming himself a convinced Darwinian, Prof. 
Dahl discusses such topics as the advantages of 
a land and of a water existence, changes of func- 
tion resulting from changes in the mode of life, 
and the physiological meaning of bilateral sym- 
metry. The forms of appendages and eyes are 
next dealt with, though we are not told why the 
sessile rather than the stalked eye is the rule in 
Arachnids, while the number of “legs” in the 
Pycnogonids is admittedly baffling. In _ his 
account of the parasitic. members of the group 
and the changes in form dependent on parasitism, 
the author is at his best; and it will be news to 
many that a pseudoscorpion is to be found on 
children’s heads hunting for other ectoparasites, 
while a mite (Tyroglyphus) lives on harmful 
fungi in the bones of birds, and is itself preyed 
upon by two species of another mite (Cheyletes). 
Finally, the question of coloration is fully dis- 
cussed, with many interesting illustrations, 
though no allusion is made to Sclater’s discovery 
of a spider that mimics a leaf-cutting ant. 
Matter and Some of its Dimensions. By W. K. 
Carr. Pp. 120. (London and New York: 
Harper Brothers, 1913.) Price 2s. 6d. net. 
(Harper’s Library of Living Thought.) 
Tus book will scarcely be appreciated by those 
who like an author to remain in touch with actual 
fact when presenting scientific achievement in a 
popular manner. It abounds with misstatements, 
such as that “bodies which emit electrons are 
known as radio-active,”’ and that ‘“radio-active 
bodies emit an emanation which . . . wholly dis- 
appears by transforming itself into electric 
particles” (p. 22). The ether, as usually in this 
type of work, plays a prominent part. It is 
described (p. 37) as a “‘jelly-like mass,” and 
“mathematicians” are said to assume that there 
are several zthers, possibly five. But the author 
supposes that they are infinite in number, and 
adds, ‘‘ We have at least conceived a method, and 
a very orderly one, by which man can evolve for 
all time, existing in each ring, or plane, or 
dimension of matter so long as he supplies the 
