1915] Middle Membrane in Wings of Platyphylax 209 
y 
one, of these processes’’; and later, ‘‘occasionally a hypodermis 
cell is seen without any such process.”’ 
At first the increase in width of the clearer layers, that is the 
elongation of the perpendicular strands and the clear spaces 
between them, causes no appreciable changes except in the 
relative width of the different layers. In certain slides one can 
see that, scattered rather irregularly in the middle membrane, 
there are a number of small ovoid bodies not well stained but 
clearly marked off from the surrounding protoplasm. At first 
it was difficult to understand just what these small bodies were 
but from a study of different stages of development it became 
apparent that they were nuclei of the hypodermal layers which 
had wandered into the middle membrane. In wings of about 
the age we are now considering, (Fig. 6), one can see that many 
of the nuclei of the hypodermis he along its inner margin, some 
are noticed protruding into the adjacent clear layer and a few 
are seen on the perpendicular strands. Those nuclei occupying 
the two first mentioned positions and some of those on the 
strands are similar in size and structure to the normal nuclei of 
the hypodermal layer, some of those on the strands however are 
seen to be much smaller and lighter stained than normal but are 
still easily distinguished by their rather distinct boundaries 
which mark them sharply off from the surrounding cytoplasm 
(Fig. 7). This enlarged view will show more clearly what hap- 
pens during this wandering and that many of the hypodermal 
nuclei pass from their original position to the middle membrane 
going from one layer to the other along the perpendicular 
strands. During this change in their position they lose their 
characteristic nuclear appearance and become much reduced in 
size. In this last figure (7) one sees, to the right, the inner ends 
of a few normal nuclei (entire nuclei not drawn) that are still 
within but at the inner edge of the hypodermal layer, adjacent 
to these are two entire nuclei that have started to move towards 
the middle membrane; the latter nuclei are as yet normal in 
appearance and size. Along some of the perpendicular strands 
can be seen other nuclei that have already decreased in size and 
lost their nuclear characteristics in a breaking up and disap- 
pearance of their reticulum and in their failure to stain. Finally, 
in the middle membrane, can be seen many of the nuclei which 
have wandered from the hypodermal layers, these have entirely 
lost their nuclear appearance but can be distinguished by the 
