28 
winglets of the larger and heaviest-bodied flies assisted the wings 
in flight, 
The wings may be described as transparent membranous 
organs, consisting of two laminz, united by veins or nervures, 
and upon their arrangement, and the form of the antenne, the 
distinguishing characters of the Diptera are formed. The several 
parts of the wings and nervures, and their differences, as seen in 
the great groups, Nemocera and Brachycera, were next described, 
and the paper illustrated by very beautiful drawings, made by Mr. 
Peake, with the Camera lucida, from preparations of the wings 
and their parts, and by microscopical preparations of the wings, &c. 
June 23rdJ.— Microscopical Section.”—Mr. T. W. Wonror on 
“¢ Tnfusoria.” 
If any vegetable or animal substance was placed in water, 
in a few days the water was found to be full of minute organisms : 
to these the name of Infusoria, or infusion animalcules, had been 
given, but many of those first called Infusoria had by latter 
observers been placed in the vegetable kingdom ; while others, at 
first named as distinct species, had been proved to be the early 
stages of higher animals, and others were now classed among a 
different group of animals. The class Infusoria was, therefore, 
much more limited than at one time supposed to be, and increased 
knowledge might prove that many more were only the early stages 
of other types of life. 
The nature of their substance, mode of development, in- 
crease, and propagation were then described. So widely were 
they distributed that scarcely anywhere can water be found 
which does not contain some Infusoria. Many will only live 
in fresh water; others are found in salt or brackish water > 
while others are only to be met with in water containing de- 
composing vegetable or animal substance. Hence water con- 
taminated by sewage matter always shows certain types. Many 
are only to be found in particular infusions, while others are 
common to several, 
Their appearance, under certain conditions, had led to 
