274 Prof. L. C. Miall and Mr. T. H. Taylor on the 
stronger and meets its fellow in the mid-dorsal line; the 
hinged plate is dorsal in position, and the descending 
branch does not aid in emergence. In the blow-fly the 
ascending and descending lines of dehiscence practically 
disappear, being represented by two minute diverging 
branches at the posterior end of the horizontal line. When 
the fly emerges the dorsal and ventral halves of the 
puparial thorax are pushed asunder, and a transverse 
rupture occurs on the dorsal or on the ventral half, some- 
times on both. Thus in the blow-fly the whole thorax 
often becomes completely detached from the puparium. 
In Oscinis frit the horizontal line of dehiscence forks into 
two branches, of which the ascending one, passing about 
half-way to the mid-dorsal region, is the stronger. At 
emergence the puparium splits open along the horizontal 
line, generally along the ascending branch and sometimes 
also along the descending one. 
In all these cases the horizontal line of dehiscence is 
constant and functional, while the transverse line may be 
slightly developed and functionally unimportant. It is 
not at all certain whether Brauer used the term “cyclo- 
rrhaphous” of the vertical or of the horizontal line of 
dehiscence, or of both. In some text-books the writers, 
evidently basing their statements on what they suppose 
Brauer to have meant, explain the term “cyclorrhaphous” 
with reference to what we have called the ascending and 
descending lines of dehiscence, making no mention of the 
horizontal one. 
The term “ orthorrhaphous ” is also at present ambiguous. 
It was originally used by Brauer * to describe a particular 
mode of dehiscence of the last /arval skin at pupation. In 
his later account + he modified his views, and it is not 
clear to us how his later definition is to be understood, 
and whether the orthorrhaphous dehiscence is a dehiscence 
of the larval integument, or of the pupal integument, or 
of both, or sometimes of one and sometimes of the other. 
It seems to us that further investigation is called for. 
Dipterologists may fairly be expected to say with some 
precision what they mean by the terms “ orthorrhaphous” 
and “cyclorrhaphous,” and to indicate the types which 
they have actually examined. 
* Monogr. der Oestriden, p. 33 (1863). 
{ Zweifliigler des kais, Museums, i, p. 7 (1880). 
