990 
true that within any given family the most 
specialized genus, and within any genus the 
most specialized species, has the largest num- 
ber of insert oculars. 
Aside from these important general conclu- 
sions, mention should be made of the occur- 
rence of what may be called “ right-oculared ” 
sea-urchins in species which normally are 
“left-oculared,” 7. e., some individuals have 
oculars I., V., II. insert, when I., V., IV. is 
the species character. Also deserving of 
special note are the remarkable peculiarities 
of the echini of the west coast of South 
America. Particular attention should be 
ealled to the invaluable tables on pages 100, 
142, 148 and 154-164 and to the diagram 
(Fig. 176) on page 153. The detailed studies 
of the development of the apical disk in 
Strongylocentrotus drobachiensis and of geo- 
graphical variation in that species and several 
others, notably Tripneustes esculentus, deserve 
far more than the passing commendation pos- 
sible here. 
A discussion of the special characters of 
genital plates occupies pages 165-173, among 
the interesting points considered being the 
exclusion of genitals from the periproct, the 
fusion and splitting of genital plates, and the 
number and position of the genital and madre- 
poric pores. The characteristics of the peri- 
proct occupy four pages and the very impor- 
tant point is emphasized that the so-called 
suranal plate is not a primitive but a secon- 
dary feature. More than twenty pages are 
filled with a discussion of the “ Aristotle’s 
lantern,” including its muscles, and the perig- 
nathic girdle which is really a part of the 
same organic system. The pits, already men- 
tioned, which were discovered in the tops of 
the half-pyramids of the Centrechinoida, are 
described here. Stress is laid on the impor- 
tance of the structure of the lantern and teeth 
for purposes of classification and the Cen- 
trechinoida is divided into three very satisfac- 
tory suborders (Aulodonta, Stirodonta, Cam- 
arodonta) based primarily on these characters. 
The fundamental differences between auricles 
and apophyses are clearly pointed out and all 
the known varieties of each are discussed. 
SCIENCE 
[N.S. Vou. XXXV. No. 913 
One finishes the reading of this first part of 
the volume with amazement at the array of 
facts it contains and with admiration at the 
way in which they are marshalled and the 
common sense with which the conclusions are 
drawn. There is no attempt to be startling 
and the newly discovered facts are not made 
the bases of wild hypotheses, but each the- 
oretical conclusion is presented with the facts 
in support of it so fairly, so open-mindedly, 
as to carry great conviction. 
To the taxonomist Part II., “ Systematic 
Classification of Echini,” which fills pages 
199-234, will prove of particular interest. The 
author begins with a brief statement regard- 
ing his inability to accept Dr. Mortensen’s 
divisions based on differences in the pedicel- 
larise and states the principles which have 
guided him. The recently suggested close 
relationship between echini and crinoids is 
emphatically disapproved, nor is any direct 
connection between sea-urchins and starfishes 
deemed at all probable. The original stock 
from which the echini have sprung is very 
likely to be found among ecystoids. The 
“Key” beginning on page 201 includes all 
the orders of echini accepted or proposed by 
the author, all the families of regular Recent 
echini and all the families and genera of the 
Paleozoic era. This key is very fully elabo- 
rated, so that it is far more than the ordinary 
key. It might perhaps be called a synopsis, 
but as it is arranged in the customary dichot- 
omous form it is very usable and will prove 
most helpful to all workers on either Recent 
or fossil echini. Nothing of the kind has 
hitherto been available and the need has often 
been sorely felt. On page 209 is given a re- 
markable “ bird’s-eye view” of the phylogeny 
of the echini as worked out by Jackson. This 
family tree well deserves most careful study 
and brings home to the reader certain funda- 
mental conclusions of the author which may 
be briefly stated here. (1) Bothriocidaris is 
- the nearest known approach to the primitive 
echinoid stock and serves as the root, or, per- 
haps better, the trunk of the tree. (2) The 
remaining characteristic Paleozoic forms are 
not in any sense ancestral to our modern 
