730 
become well.known until too late for insertion ; 
but we hope it may find a place in a future 
edition. The telephone has a chapter devoted 
to it. We wish that the theory of the instru- 
ment had been stated more at length, and are 
surprised to find not even a reference to the 
musical telephone of Reis. 
The preceding remarks apply especially to 
the latter and technical portion of the book. 
The earlier chapters, which treat of various 
theoretical matters, are less worthy of praise. 
The definitions of electrical units are in some 
cases far from clear. Some of the remarks on 
p. 96, regarding the unit of capacity, are quite 
misleading. There are also some apparent 
slips of the pen. Such, for example, is the 
statement on p. 119, that the resistance of a 
battery increases in direct proportion to the 
number of cells, which is evidently true only 
when the cells are connected entirely in series. 
To the same origin we may probably trace the 
erroneous statement on p. 94, regarding the 
use of the terms ‘ weber’ and ‘ weber per sec- 
ond.’ The chapter on electrical measurements 
seems rather to be compiled from text-books 
than derived from the writer’s knowledge of 
such experimentation, and hence fails to have 
the suggestiveness that is found in some portions 
ofthe book. The few pages devoted to electro- 
therapeutics are unworthy of the title, and do 
not deserve insertion in a separate chapter ; 
and more discrimination might well have been 
employed in the descriptions of the various 
electric lamps. The question-and-answer style 
is a disadvantage, which would be removed by 
the substitution of proper marginal titles. 
A NEW CLASSIFICATION OF THE 
MOLLUSCA. 
Encyclopaedia Britannica. 9th ed., vol. xvi., pp. 
632-697. Article, Mollusca. By E. Ray Lan- 
KESTER. 
As arule, it is hardly in the ponderous tomes 
of an encyclopaedia that one looks for new, 
fresh, and breezy contributions to biology, or 
for epoch-making articles on biological topics. 
One rather expects the carefully weighed and 
sifted results of investigation which has already 
borne the test of publication and discussion, 
prepared for general comprehension by a divest- 
ment of all unnecessarily technical terms. In 
the present instance, whatever be the feelings 
of the layman who may refer to it, the scien- 
tific student of the Mollusca will be agreeably 
disappointed. It is rumored that the distin- 
guished author has in preparation a manual of 
the invertebrates, of which it may be assumed 
SCIENCE. 
[Vor. IIL, No. 71. 
this article is the forerunner. For this reason, 
even in our limited space, which forbids a really 
thorough discussion of so large a topic, it is 
desirable that the attention of specialists should 
be called to it. 
The school of which Professor Lankester is 
one of the leaders is marked by certain well- 
recognized features. ‘They have broken away 
from the fetters of all previous zodlogical clas- 
sification. Armed with the latest instruments 
and methods, they attack biological problems 
with ardor, and rarely fail to add materially to 
our knowledge, whatever be the subject treated. 
A new biology has arisen, and the gospel there- 
of is pedigree. By their ancestral trees shall 
ye know them, under whatever adult garb they 
may conceal themselves, — this is the new law 
of the new prophets. 
So great a truth is contained in it, so rich the 
harvest under its stimulation, and so unani- 
mously has it governed the generation first 
brought under its beneficial influence, that 
even yet to doubt its infallibility and ubiquity 
of application is to stigmatize one’s self as a 
biological Philistine. Nevertheless, it is becom- 
ing pretty generally admitted that the relations 
of pedigree fail, in many cases, to express ade- 
quately the relations of adult animals as we 
find them in nature; and that the genealogical 
stand-point, like any other single stand-point, 
taken by itself, is inadequate to the broadest 
and truest view. 
Professor Lankester’s work has the merits 
of his school in a very decided degree, while 
some of its faults are equally well marked. 
These we shall endeavor to point out, though 
limitation of space will compel us to do much 
less than justice to both. 
‘¢ The Mollusca,’’ he tells us, ‘*‘ form one of 
the great phyla or sub-kingdoms of the animal 
pedigree or kingdom.’’ After a very slight 
sketch of the history of molluscan classification, 
the works of Woodward and Bronn are men- 
tioned with deserved approval, the latter being 
termed ‘+ the most exhaustive survey of exist- 
ing knowledge of a large division of the animal 
kingdom which has ever been produced ; am 
which would be true, if, for ‘ existing knowl- 
edge,’ we were to read, ‘ knowledge existing 
twenty years ago.’ Notwithstanding its great 
merits, the work of Bronn is now antiquated 
in many respects, as well as out of print, yet, 
so far, has found no worthy successor. If to 
the admirable and careful exposition of previ- 
ous systematic work, characteristic of Bronn’s 
monograph, Professor Lankester will join the 
biological results of the last twenty years, bring- 
ing both up to date, he will merit even higher 
