RELATION OF BURSARIA TO FOOD 47 



water and kept in moist chambers. Records were taken noting the 

 presence or total absence of ink and presence or completion of digestion 

 of the extracted yolk at one hour intervals beginning mth three and 

 one-half hours up to twelve hours after feeding; three more records 

 were taken at twenty-four, thirty-three and forty-eight hours. The 

 results are expressed in curves in figure 6. Curve A represents the 

 extrusion of ink; curve B, that of complete digestion of yolk. 



It is seen from the relation of the curves that even in this 

 case the ink is extruded before digestion of the extracted yolk 

 is complete, provided that a sufficient quantity of yolk has been 

 eaten. 



It was noted that a short time after the ink had been 

 eaten it became assembled into one or several rather definite 

 lumps. This takes place before extrusion. Closer observation 

 further revealed the fact that when ink particles came to be 

 included in vacuoles containing yolk they were not extruded 

 until the food of those vacuoles had been digested, while those 

 which were not included by the yolk vacuoles were very soon 

 extruded. This fact can readily be made out while one follows 

 such experiments as Experiment XXVI above. Bursaria there- 

 fore has a power of simultaneous selective extrusion of the con- 

 tents of different vacuoles as well as a power of selection in the 

 feeding process. This mechanism obviously compensates for the 

 lack of a perfect discriminative and selective function of the 

 oral apparatus. 



The results of an experiment (fig. 7) where these facts were 

 taken into account for the purpose of expressing them in a graphic 

 way in curves, is given in the following experiment. A control 

 for comparison was also kept in this case (fig. 7, curve C). 



Experiment XXVII. Forty-eight individuals were used in each of 

 both the experiment and control. The control (curve C, fig. 7) which 

 was fed ink only, shows a sharp early maximum of extrusion from 

 five and one-half to seven and one-half hours after feeding, with three 

 or four individuals retaining traces of ink as long as ten and one-half 

 to twelve hours. Curve A represents the extrusion of ink in the forty- 

 eight individuals fed both ink and extracted yolk. It shows two max- 

 ima exactly similar to those of curve A in Experiment XXVI. Curve 

 B (fig. 7) represents the course of complete digestion of the yolk in 

 the same individuals as those of curve A. There is only one maximum 



