4-6 Wisconsin Academy of Sciences, Arts and Letters. 
terior opening of the appendix (Fig. 7, app ). The chitin be¬ 
comes gradually thinner as it bends upon itself, and then ex¬ 
tends anteriorly as an outer chitinous intima of almost uni¬ 
form thickness. This outer intima is covered with numerous 
blunt projections, which do not disappear until near the place 
of union with the mid-intestine. Here it gradually becomes 
thinner, and finally is replaced by the striated intima of the 
mid-intestine (Fig. 7, sm). In most of the longitudinal sec¬ 
tions, the outer chitinous intima was separated from the un¬ 
derlying cellular layer, a peculiarity which Bordas (5) has also 
noticed. In the tubular part of the appendix, the epithelial 
cells are very much flattened, with cell boundaries not discern¬ 
ible. Each cell contains a single ovoid nucleus which has its 
long axis parallel to the chitin. These epithelial cells con¬ 
tinue as such around the posterior opening of the appendix, but 
gradually increase in size anteriorly and finally are replaced 
by the long, cylindrical epithelial cells of the mid-intestine. Be¬ 
tween the two epithelial layers of the appendix is a narrow 
space which is filled with connective tissue (Fig. 7, cct ). At 
the anterior part of the appendix, numerous branches from the 
external longitudinal muscles of the gizzard attach to the inner 
chitinous intima. 
Bordas (5) determined experimentally the function of the 
appendix in Vespa. His results, which are of special interest, 
are as follows:—“Das Zuriicktreten der Habrung von 
hinten nach vorne zu verhindern, d. h. vom Mitteldarm 
wahrend dessen peristaltischen Bewegungen zum Kropfe, fallt 
im besonderen dem wurmformigen Appendix zu, der der Darm- 
klappe bei den Apidae und anderen Insekten entspricht. Ich 
habe tatsachlich experimentell festgestellt, dass der Biicktritt 
der Hahrung unmoglich ist. Es geniigt hierfiir eine gefarbte 
Eliissigkeit in den Mitteldarm von Vespa zu injizieren. Ubt 
man dann einen Druck von hinten nach vorne aus, bemerkt 
man, dass nicht ein Tropfen der Fliissigkeit in dem wurni- 
formigen Appendix gelangt, und dass sie sich zwischen semen 
aussern Wanden und denen des Mitteldarmes anhalift. tiber- 
dies ist es leicht einzusehen, dass, je grosser der auf die Eliis- 
sigkeit ausgeiibte Druck ist, diese umsomehr die Wande des 
