No. 378.) REVIEWS OF RECENT LITERATURE. 433 
that which development had pursued ; also, it is not reversible — that 
is, an organ once lost cannot reappear, nor can a degenerate rem- 
nant again fully develop. 
Regressive evolution is caused by the limitation of the means of 
subsistence — food, capital, or forces for work. In biology it has 
for its principal if not its only factors, the struggle for existence 
between the organs and the struggle for existence between the 
organisms. In sociology artificial selection plays a preponderating 
‘role, natural selection a secondary one. The occasional causes of 
regressive evolution are inutility of function, the insufficience of 
nutrition or of resources, and, in biology alone, the lack of room. 
An institution or an organ which has ceased to be functional and 
has lost all utility, direct or indirect, persists, however, if one or other 
of the factors of atrophy, variability, or selection is not at work. 
The book is written in an interesting, somewhat popular style, and 
is illustrated by numerous figures in the text. 
ZOOLOGY. 
The Mammals of Florida.1— In Mr. Bangs’s recent account of . 
the mammals of peninsular Florida and the coast region of Georgia 
we have the first attempt at an exhaustive enumeration of the mam- 
mals of a definite geographical area from what may be termed the 
point of view of the new era in the history of North American mam- 
malogy. It therefore gives a good opportunity of contrasting the 
new with the old in this field of research. Of papers based on large 
collections of mammals from restricted areas, and also of mono- 
graphic reviews of particular groups, there has been no lack in recent 
years, but none has before attempted to treat exhaustively the mam- 
malian fauna of a well-defined and considerable area. 
It is needless to say that Mr. Bangs approaches his subject from 
the radical point of view of the “new school,” and it is therefore of 
interest to contrast our knowledge of to-day, as here reflected, of the 
mammalian fauna of Florida with that of, say, twenty years ago. 
Fortunately, Mr. Bangs’s ‘Comparative Table” of the principal 
Previous lists of the mammals of the region under review renders 
l Outram Bangs, The Land Mammals of Peninsular Florida and the Coast 
Region of Georgia, Proc. Boston Soc. Nat. Hist., vol. xxviii, No. 7, March, 1898, 
PP- 157-235, with text cuts. 
