984 
he duly describes. In all, 72 genera are recog- 
nized, of which 25 were first named by Mr. 
Simpson, while many others, credited to vari- 
ous authors, were first properly defined by the 
same writer. All this amounts to a revolution 
in naiadology, comparable with that produced 
by Pilsbry in the study of the Helicide. 
Of interest to general biologists will be the 
map given showing the distribution of the 
naiades. In the Old World the regions of Scla- 
ter and Wallace are respected by the fresh- 
water mussels, except that New Guinea goes 
with the Oriental region, as also do Japan, Corea 
and Manchuria. In America the neotropical 
region is valid for naiades, but North America 
is divided into three primary regions, the At- 
lantie, the Mississippi and the Pacific, but the 
last is considered a part of the Palearctic! In 
all about 1,117 species are recognized, many 
having long lists of synonyms. Concerning the 
innumerable so-called species described from 
France by the followers of Bourguignat, Mr. 
Simpson says: ‘‘ Life is too short and valuable 
to be wasted in any attempt at deciphering 
such nonsense, and I have not even cumbered 
the pages of this work with a list of these new 
species.’’ It is indeed unfortunate that the 
interesting character of the European fauna 
should be obscured by the treatment it has re- 
ceived at the hands of its students. The fresh- 
water mollusca, in particular, exhibit a won- 
derful polymorphism, which in the highest 
degree merits the attention of the evolutionist ; 
but when every varying phase is designated a 
species the result is mere chaos. WhenI lived 
in England, I knew of a number of ponds pro- 
ducing special forms of Limnea (particularly L. 
stagnalis), which were so different that they 
could be recognized at a glance ; one of the most 
distinct of these varieties abounded in a pond 
no bigger than a large rug, and was found no- 
where else. The same sort of thing is true of 
the European naiades, and a careful compara- 
tive study of all the forms called species by the 
Bourguignat school, with an account of the sey- 
eral conditions under which they exist, would 
be an extremely valuable contribution to bi- 
ology. 
As is inevitable in so great a work, a few 
errors of nomenclature occur. The new genus 
SCIENCE. 
(N.S. Vou. XIII. No. 338. 
Dromus will be considered by some too similar 
in name to Dromius, Bon., but I think it should 
be allowed to stand. The genus Nodularia 
Conrad, 1853, is preoccupied by Nodularia 
Oken, 1815. This will apparently oblige us to 
call the genus Lanceolaria Conrad, with Lan- 
ceolaria grayana (Lea) as the type, while the 
section of L. douglasix (Gray) can be called No- 
dularidia n.n. On-p. 851, Ptychorhynchus in- 
certus should be P. murinus (Heude), and on p. 
897, Spatha tristis should be S. rochebrunet 
Jousseaume. 
T. D. A. COCKERELL. 
East LAs VEGAS, N. M., May 12, 1901. 
SCIENTIFIC JOURNALS AND ARTICLES. 
THE leading article of the Botanical Gazette 
‘for May is the ‘Genetic Development of For- 
ests of Northern Michigan, a study in Physio- 
graphic Ecology,’ by H. N. Whitford. The 
factors that influence tree growth are divided 
into three groups—climatic, ecologic and his- 
torical. Favorable climatic factors make pos- 
sible a forest formation ; ecologic factors bring 
about the plant society condition ; and the his- 
torical factors, by changing the physiographic 
features, change the plant societies. The life 
histories of five series of plant societies are dis- 
cussed, viz., sand, clay, rock, swamp and 
clearing societies. In four cases there is a grad- 
ual progression from xerophytic societies to a 
mesophytic forest. In the case of the swamp 
the progress is from hydrophytic societies to 
a mesophytic forest. The article is illustrated 
with eighteen half-tone reproductions of photo- 
graphs. E. W. D. Holway contributes his third 
paper on ‘Mexican Fungi,’ in connection with 
Dr. Dietel, describing thirty-one new species of 
Uredinee. Mr. G. M. Holferty gives the re- 
sults of his study of the ovule and embryo of 
Potamogeton natans, clearing up a number of 
gaps in our knowledge of this primitive mono- 
cotyledonous type. Thepaper is illustrated by 
two excellent plates. Mr. Charles T. Druery, 
of London, writes upon ‘Fern Variation in 
Great Britain,’ and calls the attention of Amer- 
ican students to the great scientific value of 
looking after fern ‘sports.’ Mr. D. G. Fair- 
child, agricultural explorer of the U. 8. De- 
