84 ENTOMOLOGICAL NEWS. [Feb., 14 
group are usually stated. Thus the characters of the Submerged Vege- 
tation Association are “in being distinctly aquatic and also essentially 
independent of the bare bottom and of the surface,” but “strictly de- 
pendent upon the vegetation for nesting places, shelter, etc. The mud 
minnow has been studied experimentally and shows avoidance of 
light.” The tendencies of this same association are toward change: 
“This association, like all the others, is destined not to last; changes 
are taking place all the time. The chara is filling the pond at the rate 
of one inch a year and is making a fine soil for roots of other plants. 
As soon as the dense chara stage has existed for a time we find other 
plants, such as Myriophyllum, Potamogeton, and water lilies. As soon 
as these have become established we have the commencement of the 
next association.” Finally, the succession of animal life in the same 
pond and the fate of the pond itself is considered and illustrated with 
tables showing the occurrences of species in ponds of different ages. 
The terms “formation,” “association” have here a technical ecologi- 
cal significance and, just as there is a well-known series of taxonomic 
groups of increasing magnitude (species, genus, family, order, class, 
phylum), so there is employed in this book a series of ecological 
groups, also of increasing magnitude (mos or mores, consocies, 
stratum, association, formation, extensive formation) which, with the 
exception of the first, bear not “the slightest relation” to the taxonomic 
groups. They are defined on pages 37 and 38 but, we suspect, with no 
greater exactness than has attended attempts at definition of the 
taxonomic groups. 
As may be seen from the resumé of the Pond chapter, change in 
nature is emphasized throughout, the phenomena are dynamic, not 
static. Ecological succession is often met in different parts of the book, 
especially on pages II0-124. 
An interesting discussion is that of the efforts of ecologists, geog- 
raphers and climatologists to find a method of measuring the environ- 
ment of organisms which shall include a number of the most important 
environmental factors. Dr. Shelford concludes that “the evaporating 
power of the air is probably the best index of environmental condi- 
tions of land animals” (p. 164). 
The author is best known to entomologists by his excellent work on 
tiger beetles, but these are by no means the only insects employed in 
characterizing ecological groups. The Index of Subjects is so ar- 
ranged that one can quickly ascertain what members of a given group 
are mentioned in the book. Thus under “Flies or diptera” are refer- 
ences to fifty-one names of families and genera, alphabetically ar- 
ranged. Almost all of the orders of insects, some of the Arachnids 
and some Myriopods are represented, so that the book contains much 
of interest to the entomologist. 
Owing to the numerous species cited and figured, the book is one 
