218 
G. ARNOLD. 
of Physiology in tliis University, for valuable advice on 
staining for fat with Nile blue sulphate. 
Conclusions. 
Digestion in Planaria lactea, and probably in all 
Triclads, is both inter- a,nd intra-cellular. 
The intercellular digestion is limited to fat. Tlie fat is 
broken down in the lumen of the intestine by the secretion 
of tiie goblet-cells into fatty acids, which are then absorbed 
by the columnar cells and synthesised again into neutral 
fat. 
Most of the fat is digested in the cytoplasm of the columnar 
cells, but some of it is extruded into the parenchyma at their 
base, and appears in the yolk-cells and in the wandering 
cells. 
The digestion in the vacuoles takes place in an acid medium, 
as evidenced by the change in the staining reaction of 
ingested leucocytes. 
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