1915] Middle Membrane in Wings of Platyphylax 203 
finds a delicate membrane lining the whole interior of the wing 
bags. This is the ‘Grundmembran’ of Semper.’’ The figure 
to which Mayer refers for illustration of the middle membrane 
is taken from what he labels a mature larva; it is very similar 
to what we have shown in figure eight which is of an early pupa, 
this does not show any thing so membrane-like as Mayer has 
drawn and called the ‘Grundmembran’ in several of his later 
figures. Again he says: ‘The inner ends of these spindle- 
shaped cells are often seen to be fused to a double membrane 
(middle membrane), occupying the space between the two walls 
of the wing pad. In very old larve, however, this membrane is 
usually absent, and the inner portion of the cells which 
constitute the wing tissue end free.” 
Tannreuther (11), working with Lepidoptera found that 
“‘the basement membrane of the larval hypodermis is contin- 
uous over the sides of the evaginated cavity, which in later 
stages of development becomes the middle membrane of the 
larval wing. The hypodermal cells with their long fibre-like 
threads remain attached to the basement membrane which is 
continuous with that of the hypodermis.’”’ Again, in speaking 
of the larva in the fourth instar, he says: ‘‘The basement 
membrane is not so distinct, as the larva (e) at this stage differ 
in the sharpness of this membrane. In some individuals it is 
scarcely visible, in others it can only be determined by the ends 
of the hypodermis cells or fibres.”” In speaking of the prepupal 
wing he says: ‘“‘The basement membranes of the evaginated 
cavity become united to form the middle membrane of the 
adult wing.”’ 
The following quotations are from Krtiger whose work was 
principally with Coleoptera. ‘‘Dort wo die beiden Fltigella- 
mellen aneinanderstossen, zeigt sich schon, wie bemerkt, die 
erste, schwache Bildung einer Grundmembran. Sie geht offen- 
bar aus den Zellen der Hypodermis hervor, was allerdings erst 
in spateren Entwicklungsstadien klar erkannt wurde. Die 
Grundmembran ternnt noch als deutliche Scheidewand bei die 
Flugellamellen.”’ 
Powell (7) in his work on the development of the wings of 
certain beetles, speaking of the larve shortly before pupation. 
“The basement membrane which throughout the development 
of the wing is very thin and not easily discernable, becomes 
