124 CYTOPLASMIC INCLUSIONS 



enzymes actually present. In A. proteus, Mast and Doyle (1935b) find 

 that the mitochondria accumulate around the food vacuoles six to eight 

 hours after its origin and then again at sixteen to thirty hours (Fig. 30) . 

 During the first contact, digestion begins, starch is changed to erythro- 

 dextrine, and fat leaves the vacuole. In the second contact, vacuole re- 

 fractive bodies and crystals disappear. These authors never found the 

 mitochondria actually entering the vacuole. The relationship between 

 mitochondria and starch digestion vv'as directly demonstrated by Holter 

 and Doyle, who showed that these granules contain amylase. Their 

 function is restricted with respect to digestion, since they lack dipeptidase, 

 according to similar studies by Holter and Kopac (1937). This situa- 

 tion is not universal, since Hopkins (1938b) also working with Mast, 

 showed that no formed granules are associated with digestion in the 

 marine amoeba, Flabellula, although a material is dissolved in the 

 vacuoles which when precipitated by disturbance, and so forth, forms 

 granules which stain with Janus green B and other mitochondrial stains. 

 Again, in many other Protozoa the mitochondria have no direct con- 

 nection with digestion. Thus mitochondria may contain enzymes in some 

 cases, but this is not a necessary association. 



Excretory granules associated with contractile vacuoles have been 

 described many times, but only recently have mitochondria been proved 

 to be associated with the excretory process. Mast and Doyle (1935a) 

 have shown that the excretory granules of A. proteus (Figs. 24, 25, 47) 

 correspond in their staining reactions to mitochondria. By centrifuging 

 the majority of these bodies into one end of the amoeba and removing 

 this part, these authors showed that the formation of the vacuole is 

 dependent upon these granules and that if most of the mitochondria 

 are removed, death follows. In one experiment, most of the mito- 

 chondria were left, with the result that the average interval between 

 pulsations was 3.46 minutes. If few mitochondria were left, the time 

 was correspondingly longer, and when very few granules were left, 

 the average time between pulsations increased to twenty-five minutes. 

 Mast and Doyle interpreted these experiments as indicating that some 

 excretory material, toxic to Amoeba, is eliminated by the vacuole, and 

 that the mitochondria function as the means of transport to the vacuole. 



Doyle (1935) harmonized the apparently discrepant functions of 

 digestion and excretion by pointing out that they may be united under 



