66 Psyche [April 
delphax, so far as I have had the opportunity to ascertain, and in 
these genera the diverticulum does not enclose other portions of 
the alimentary canal. But although the alimentary canals of 
these Homoptera are all on the same plan, yet the simple arrange- 
ment of Aleyrodes and Psyllid seems to lead up to and culminate 
in the very complex system of Cercopid and Cicada. On con- 
sidering the diverticula and zigzags of these two latter one must, 
I think, conclude that Berlese’s theory (of filtration or osmosis in 
order to get rid more quickly of imnutritious liquid) is correct. 
Dr. Licent’s opinion that the anterior portion of the malpighian 
tubes is producing the froth or spume of the nymph is, in my opin- 
ion, certainly correct. 
The alimentary canal of the nymph of Tomaspis, when just 
hatched, is practically like that of the adult, so that the enwrapping 
of other parts of the midgut by the diverticulum takes place in 
the embryo. There is a well-marked cesophageal valve, and 
behind and laterally to this the midgut forms a recurved diverticu- 
lum or pouch somewhat U-shaped in transverse section, the ex- 
ternal cavity of the pouch enclosing the zigzag ascending anterior 
portion of the midgut and descending straight portion; also the 
straight ascending and zigzag descending portions of the malpi- 
ghian tubes. But the whole pouch and all parts of the alimentary 
canal are covered by the peritoneal membrane, muscular and con- 
nective tissues. Thus the zigzags of the various parts of the gut 
do not pierce the walls of the pouch in order to enter or leave it, 
but are merely enclosed between its exterior walls (fig. 1, d’, ex), 
the peritoneal membrane, muscular and connective tissues sealing 
up their entrances and exits and the narrow gap or slit-like open- 
ing (fig. 1, d’, so) between the exterior walls of the pouch. I thus 
differ from Dr. Licent in believing that the basement-membrane 
of the epithelium of the pouch does not separate or split off there- 
from and enclose the other portions of the midgut, but that it is 
the peritoneal membrane which encloses the whole hermetically. 
The pouch is a diverticulum of the midgut, and the lips of its long, 
narrow internal aperture leading from the pouch to the sac are 
bounded by a broad and thick band of fat-cells (fig. 3, f) on each 
side, which may probably act as a valve to regulate the flow of 
food from the pouch to the sac; and as the latter is somewhat 
askew to the large and more or less conical sac of the midgut, the 
