1884.) Recent Literature. 609 
— The study of these problems, we would add, will tend to 
throw light on the life and death of species, of genera, families 
and orders of plants and animals. 
At present the causes of the extinction of the life of species and 
higher categories are interwoven with those of the origin of species. 
To say that species like individuals have their appointed time is a 
mere platitude. It is now beginning to be understood that geo- 
ical extinction was due mainly to changes of land and water 
in the growing continents, and to consequent lack of adaptation 
to the new conditions on the part of those organisms which were 
unsuccessful in the struggle for existence. Thus the apparent 
lack of continuity in a part of the life which stocked the earth in 
former ages was due to the lack of adaptation. But life as a 
whole has always been continuous, perennial; the breaks were 
the result of more or less local breaches of continuity in the con- 
tinent-making processes. The youth, maturity and senility of 
ndividuals is, as Hyatt has shown, paralled by the youth, matu- 
nty and decline of the types to which they belong; and we can 
now begin to see how correlated and continuous are the phases 
of what we call life and death in the material world, and through- 
out all time, and all forms of life. 
20% 
RECENT LITERATURE. 
Braver’s Stupies ox Diprerous Larvæ'—This is a most val- 
uable addition to our knowledge of the early stages of the Dip- 
tera, and is the result of a large acquaintance with the early forms 
of this order, by one who has for over twenty years devoted spe- 
na attention to these insects. In his “ Monographie der (Estri- 
den, 1865, but more especially in his “ Kurze Characteristik der 
) en-larven,” 1869, wide gaps in our knowledge of the trans- 
| lons of the Diptera were filled. And now with the present 
- Work, in addition to the observations of the earlier entomologists, 
a recent writings of Fritz Miller, Dewitz and Wierzejski 
on th formations of the Blepharoceridz, and of Handlirsch 
tt Nemestrinide, we are in possession of a knowledge of the 
wi Stages of one or more species of all the natural families of 
era. After lengthy remarks on the systematic relations of 
t groups of Diptera, based on the larval characters, Brauer 
typical, inherited feature in the entire group 0 
ipteren-larven nebst einer zusammenstellung von Beispielen 
über dieselben und beschreibung neuer Formen. Von Prof. Dr. 
Tafeln. Besonders abgedruct aus dem XLVII Bande de 
l. k. Akad. der Wissensch. Wien, 1883; 4to, pp. 100. 
