The First Abdominal Segment of Embryo Insects. 
103 
or during revolution. The canals and spaces alluded to in Ayers’ descrip¬ 
tion are exactly like those seen in Periplaneta in the corresponding stage, 
and must not be regarded as delicate ramifications of the body cavity but 
as irregular spaces produced by the falling asunder of the columnar cells. 
They are probably identical with the intercellular vacuoles seen in the de¬ 
generating pleuropodia of Blatta and Periplaneta. Had Ayers passed 
sections through the pleuropodia of Oecanthus before the setting in of 
dissolution, his description would have been different and very probably 
like what I have given for Xipliidium. 
Stenobothrus. 
Graber briefly described the pleuropodia of this Acridian in his paper on 
polypody [’88]. In a more recent article [’89] he gives a fuller description 
which I reproduce: 
“ Each of the pleuropodia of Stenobothrus at the time of its greatest de¬ 
velopment lies on the pleural wall of the first abdominal segment about 
where, in later life, the tympanal apparatus is situated. It is a flat¬ 
tened biscuit-shaped body about 1 mm. in diameter. While the remainder 
of the body wall remains destitute of pigment till the insect hatches, the 
pleuropodia acquire a brownish hue. Of the same color also is a finely 
granular coagulum partly glued to the skin in the immediate neighbor¬ 
hood of the pleuropodia and the legs. In sections the organs present a wide 
cavity which opens by means of a short and rather broad passage into the 
body cavity. In some sections a few cells, probably interpretable as blood 
corpuscles, are to be found in the cavity; in other sections these cells are ab¬ 
sent. The large cells of the outer wall, which in this insect also are enorm¬ 
ously developed, are especially interesting, as they are so filled with yellowish 
granules that the whole outer wall of the sack presents the appearance of 
a brownish yellow plate. These granules are visible even in Canada 
balsam preparations. Closer observation shows that the above mentioned 
coagulum in the vicinity of the pleuropodia and legs contains yellow 
granules very similar to those contained in the cells and thus justifies the 
conclusion that this coagulum, at least in part, is secreted by the pleuro- 
podial cells, the outer surfaces of which are not covered by a chitinous 
cuticle.” 
Blatta germanica, L. 
Patten was the first investigator to describe the pleuropodia of Blatta 
germanica [’84], His observations are summed up in the following words: 
“ At first a number of abdominal appendages are developed which, how¬ 
ever, quickly disappear again with the exception of the first pair, which 
further develops into pear-shaped structures attached to the abdomen by a 
stem that increases in length and finally changes into a very fine duct 
leading into a small cavity in the expanded distal extremity, which owes 
