JUNE 14, 1901.] 
with even more force to the topic of acetylene. 
Strangely enough, no directions are given for 
the photometric testing of gas (save for street 
testing), so that for this important measure- 
ment recourse must be had to another book. 
From a typographical standpoint too, the book 
leaves something to be desired ; several of the 
cuts, for example, Figs. 43, 204, 207 and 211, 
are not clear. 
The work in the main is excellent and should 
be in the library of every one interested in the 
subject of gas. : 
Aucustus H. GILL. 
Lehrbuch der vergleichenden Anatomie der Wirbel- 
losen Thiere. Yon ARNOLD LANG. 2te aufl. 
Iste lief. bearbeitet von Dr. KARL HEs- 
CHELER. Jena, Gustav Fischer. 1900. Pp. 
viii + 509, mit 410 abb. 
In this volume is included the molluscan part 
of Lang’s well-known and useful work, en- 
larged, revised and additionally illustrated. 
The difference between the original or the 
excellent translation of Bernard (Macmillan, 
1896, pp. 288, ills. 222) is not so great as the 
figures seem to imply, and is largely accounted 
for by the increased size of the type and the 
addition of 188 new cuts. A brief summary of 
the chief additions may be useful. 
In the ‘systematic review’ we find the se- 
quence of the orders changed in the Gastropods, 
and, in the Pelecypods, a number of suborders 
introduced ; while the unnatural and illogical 
orders of the Pelseneerian classification, and his 
jumbled-up collocations of families under them, 
are still retained, though a synopsis of later 
views is included. In the review of ‘superfi- 
cial organization’ the Amphineura are recog- 
nized as a class and a short chapter on the 
Cephalopod shell is added. 
Under ‘ pallial complex,’ reference is made to 
the discovery of gills in certain fresh-water 
pulmonates which is further enlarged on under 
‘Respiration,’ and the characters of. the Janel- 
lids, not referred to in the first edition, are 
discussed. The chapter on respiration is en- 
larged and a general summary appended. 
A few remarks on Spirula are added under 
‘Musculature,’ and under ‘Asymmetry’ new 
information is added and the author’s theory 
SCIENCE 
945 
discussed in the light thus thrown on the sub- 
ject, with a reference to the bibliography for 
the opinions of others on this topic. 
The phosphorescent organs form the subject 
of an appendix to the ‘sensory organs,’ and, 
under ‘alimentary canal,’ additional informa- 
tion is given on the proboscis in Conus, Terebra, 
Cassis, Dolium and Pyrula. 
The general discussion on the intestinal 
region, stomach and hepatic glands is somewhat 
enlarged. The asserted absence of endothelial 
investment in the alimentary canal and digestive 
glands is alluded to, and the general discussion 
of the nephridia has been enlarged. 
Under ‘ Reproductive Organs’ we find addi- 
tional matter in the general discussion, and also 
relating to the Ascoglossa and Holohepatica, 
among the Nudibranchs, and the Stylommato- 
phora among the pulmonates. 
The chapter on the ‘ Parasitic Gastropods’ 
has been expanded and notes on Thyca and 
Mucronalia added. 
Under ‘ Ontogeny’ we note additions in con- 
nection with Ischnochiton, Vivipara, Limaa, 
Dreissensia, Yoldia and Loligo, and the entire 
portion relating to Cephalopoda seems to have 
undergone amplification and revision. Much- 
improved indices and enlarged bibliography are 
subjects for gratitude. 
The summary of facts in relation to mollus- 
can anatomy included in this work is rich, and 
may be consulted with profit by those interested, 
though entering less into detail than the work 
of Simroth in the new edition of Bronn’s ‘ Thier- 
reichs’ which is not yet complete. 
Whether the training which most anatomists 
get is of a kind which impairs their faculties for 
generalization is a question difficult to answer ; 
but it is certain that most of the younger con- 
tributors to anatomy in mollusks have not much 
advanced the science by their simultaneous 
hypotheses bearing on classification. The cause 
seems to be that they do not realize the vast- 
ness of the untrodden field in the molluscan 
subkingdom and generalize on too limited data. 
Furthermore, other animals are often so much 
easier to handle and require so much less labor 
in investigation to afford tangible results, that 
it is not remarkable that most instructors turn 
to animals of smaller size and simpler organi- 
