DIGESTIVE PROCESSES IN PLANARF7E. 
207 
Intra-cellular and General Digestive Processes 
in Planariae. 
By 
O. Arnold, 
From the Cytological Laboratory of the University of Liverpool. 
With Plate 17. 
In 1878 Metsclinikotf drew attention to the plieuoinena 
of intra-cellnlar disfestion occnrrino' in Tnrbellarian worms. 
Since that time bnt little lias been published dealing with 
this very interesting subject. 
Metschnikoff’s short notice was followed by a paper by 
Lankester dealing with intra-cellnlar digestion in the endo- 
derm cells in the medusa of Limnocodinm, and two years 
later, 1883, Metschnikolf published further observations on 
intra-cellnlar digestion in the mesoderm cells of Synapta and 
l^hyllirhoe. 
Intra-cellular digestion has been observed in Ccelenterates 
generally, sponges. Protozoa, and in the leucocytes of the 
blood. 
Within recent years several observers have dealt with the 
digestion in the Protozoa, but apparently no work has been 
published dealing with the cytological details of intra-cellnlar 
digestion in any of the Enterocoela. 
Mouton in 1902 and Nerinstein in 1905, following on the 
earlier work of Greenwood and Saunders, have given long 
and detailed accounts of the process of digestion in Amoeba, 
Paramoecium, etc. These authors, however, have limited 
their attention almost entirely to the intimate history and 
staining reactions of the food vacuoles of those animals, and 
their conclusions afford few data which shed any light on 
