526 
HENRY LESLIE OSBORN 
ALIMENTARY SYSTEM 
The space between the oral sucker and the pharynx is occupied 
by a prepharynx, figs. 1,2. This is a very thin walled tube thrown 
into many different shapes in accord with the contractions of the 
animal, connecting between the cavities of the oral sucker and the 
pharynx. In many cases a small conical point projects forward 
into the base of the cavity of the oral sucker (figs. 1 and 2). At 
this part the wall is furnished with circular fibres (nis) which act 
as a sphincter. Behind these the wall is supplied with longitud- 
inal muscles. When fully extended the prepharynx has a length of 
about 0.06 mm. 
The pharynx is well seen in the surface views in figs. 1 and 2. 
In the whole animal from which fig. 1 was drawn there seems to 
have been no retraction of the anterior end, such as is seen in many 
of the preparations. In fig. 3 the organ lies transversely to the 
axis of the body and is less normal than the position in fig. 1. 
The pharynx measures 0.7 mm. in length. It is somewhat 
flattened from side to side measuring 0.03 mm. and 0.07 mm. 
in its lesser and greater diameters. Its wall has the usual mus- 
cular structure. 
The oesophagus is surrounded by a layer of cells. They are 
very indistinct in all my preparations but apparently they are 
0.01 mm. in length and pyriform tapering toward the passage. 
Their deeper ends form a somewhat distinct boundary for the 
mass, in which the rounded ends of the cells can be seen, lodging 
nuclei of a constant size. These have a sharp membrane and a 
large and distinct nucleolus, and are clear and nearly devoid of 
chromatin. The cells in the parts nearer the lumen of the oesoph- 
agus lose their boundaries and the mode of connection with the 
oesophagus cannot be seen. 
Cells are found in this position in many trematodes and are 
often referred to as salivary glands. Otto ('96) calls attention 
to a view of Leukart's that they are more likely to be parenchyma 
cells employed in the secretion of the cuticle, and favors this view. 
Notwithstanding the absence of physiological and histological 
evidence it still seems best to designate these cells oesophageal 
glands. 
