Studies on the Life History of Protozoa. 437 



the vacuole the food is brought into the immediate vicinity of the 

 macronucleus where the effect of the nuclear environment is 

 shown by the immediate acid reactions with congo-red of the 

 vacuole contents (Wallengren). The food material in such a 

 vacuole is massed into a more or less homogeneous body corre- 

 sponding to Greenwood's observation on Carchesium, and in this 

 condition the digestive fluids work upon it to resolve it into 

 digestible and indigestible parts. After this the soluble portions 

 are absorbed and the residue defecated. The soluble portions 

 pass into the endoplasm to be stored up as reserve food (Wal- 

 lengren) from which they are taken as the need comes to be 

 made into living molecules. 



The processes of digestion thus given rise to definite elements 

 in the endoplasm, elements which react to stains in characteristic 

 ways. In addition to these, however, we might expect to find 

 waste matters due to incomplete oxidation as well as final products 

 of metabolism in the form of crystals, etc. The various possibili- 

 ties of this nature have given rise to different interpretations upon 

 which my own observations throw but little additional light. 

 With neutral-red acting upon the organism when alive, Prowazek^ 

 distinguished three kinds of granules in the endoplasm: (i) The 

 food balls; (2) Small round granules which are distributed 

 throughout the periphery more or less uniformly (Prowazek 

 actually found them at the two extremities and about the mouth); 

 (3) Minute granules distributed throughout the endoplasm and 

 all over the body. 



The minute peripheral granules (No. 2) are interpreted by 

 Prowazek in the same way that Wallengren had previously inter- 

 preted similar bodies in Pleurocoptes hydractinicB, viz., as excre- 

 tory vacuoles with a solidified granule of excreta within them. 

 Piitter,2 on the other hand, interpreted them as basal bodies of 

 centrosome nature lying at the bases of cilia. Wallengren subse- 

 quently showed, however, that the granules in question are not 

 at the bases of cilia but lie beside the cilia, and that rows of these 

 granules alternate with rows of cilia. He interpreted them as the 



^ Vitalfiirbung mit Neutralrot an Protozoen- Z. wiss. Zool. Bd. 63, 1898. 

 ^ Studien iiber Thigmotaxis bei Protisten. Arch. f. Anat. u. Phys. 1900. 



