378 SUMMARY OF CURRENT RESEARCHES RELATING TO 



also inquired into the process of extrusion. The liquid of the newly 

 formed food vacuole is partly made up of the external medium and 

 partly of an acid secreted by the base of the buccal pouch. After a 

 few minutes this liquid is absorbed and the vacuole membrane becomes 

 applied to the yolk grain. The vacuole contents remain acid in 

 reaction throughout the process of digestion of vitellin and yolk grains. 



Sooner or later after the initial absorption of liquid about a grain, 

 digestion begins. Digestion may or may not result on the second 

 appearance of liquid in the vacuole, according to the principle that 

 whenever the rate of solution— this perhaps in part depending upon 

 the concentration of the cleavage agent — is greater than the rate of 

 absorption, then the liquid products of digestion accumulate more or 

 less about the grain, while if the rate of solution of the grain is slower 

 than the rate of absorption, then the products of digestion are removed 

 as fast as they are formed. Equilibrium between these processes in 

 the vacuole may be established during digestion of vitellin with much, 

 little, or no liquid present in the vacuole. 



The average time for complete digestion of vitellin in Bursaria was 

 found to be directly proportional to the square root of the quantity 

 of vitelline eaten, i.e. the relation expressed by Arrhenius' formula 

 t = k V M was found to hold to within the limits of experimental error. 

 Congo red absorbed by vitellin grains and ingested by Bursaria interferes 

 with or preventSidigestion of the parts of the vitellin grain with which 

 the dye is associated and causes an early extrusion. Olein is digested 

 and absorbed by Bursaria, while paraffin oil is not affected. Lipoids 

 and fats play an important role in promoting growth in Bursaria. No 

 evidence was obtained for the formation of stainable lipoid from pure 

 vitellin. There seems to be no digestion of starch or amylum grains. 



The time of extrusion is determined by the quality (chemical) and 

 the quantity or intensity (chemical, physical, or both) of the stimulus 

 from within the vacuole by the substance eaten. The maximum 

 tendency to respond by extrusion to the stimulus from the vacuole 

 contents, exists within a limited time (4-6 hours with fresh yolk) after 

 feeding. 



Review of Euglenoidina.* — L. B. Walton takes a review of this 

 order of Flagellate Infusorians, with particular reference to the forms 

 found in the city water-supplies and in other localities of Ohio. They 

 are typically elongated ovals or spindles, with a length of 6-50" microns, 

 with a flagellum (or rarely two) arising from a cytopharynx. and con- 

 sisting of an axial filament in a plasmic sheath They show a rapid 

 rotating swimming movement, drawing themselves forward by means of 

 the flagellum, or a creeping twisting movement. There is a striated 

 periplast, and often a shell besides. A pigment spot or stigma, orange- 

 red or dull yellow, is typically present. There is usually a large 

 vacuole, with a vacuolar canal opening into the reservoir, narrowed 

 anteriorly into a cytopharynx. The large vacuole has opening into it 

 one or more contractile vacuoles. The nucleus consists of a central 



* Bull. Ohio State Univ., six. (1915) pp. 343-449 (15 pis.). 



