710 A. T. EVANS 
columnar epithelium has been described by Dahlgren and Kep- 
ner (’08, p. 65) who state that in the lobster “‘the simple colum- 
nar epithelium cells that cover the outside of the body under 
the shell, which they form, assume part of this duty [that of a 
short ligament] and acquire strength to perform it by the develop- 
ment of strong fibrils in their cytoplasm.’’ The central dis- 
sepiment cells flares out at the dorsal and ventral ends, where it 
comes into contact with the chitinous covering, and all its cells 
contain fibrils. At the lateral points of attachment of the 
flexor muscle a wing-shaped expanse of cells, which extends to- 
ward the point of attachment of the muscle, shows well developed 
fibrils in the cytoplasm of the cells. All other epithelial cells 
are of the columnar type, except midway between the dorsal 
and lateral portions, where there is a small area of cuboidal 
epithelium. 
Beginning with the dorsal portion of the central disseppiment 
and proceeding around either side of the appendage, the layer of 
epithelium changes gradually from modified columnar to simple 
columnar, then to cuboidal, again to columnar and finally to 
modified columnar epithelium in the extreme lateral region at 
the point of attachment of the flexor muscle. This same sequence 
of changes in the character of the epithelium may be noted if 
the layer of epithelial cells be followed from the lateral attach- 
ment of the flexor muscle to the median insertion of the ventral 
portion of thecentral dissepiment of modified columnar epithelium. 
The adipose and connective tissues are loosely arranged in 
the upper portion of the appendage, producing an areolar mass. 
The large flexor muscle has for its inner point of attachment a 
position about midway between the median dorsal and ventral 
ends of the dissepiment. Its outer point of attachment is the 
lateral mass of modified columnar epithelium containing fibrils, 
as well as some of the columnar epithelium which hes along 
the ventral surface of the appendage. 
The large sinuses occupying a ventral median position supply 
the appendage with blood. 
No nerve fibers or sensory cells were found in the appendage, 
but no special neurological stains were used. 
