528 W. B. HARDY. 



ingested by the apical cells, both in the body of the animal and 

 in the proximal region of the blastostyles. 



Towards the close of digestion a few free cells appear in 

 the somatic fluid. Each is rounded and composed of dark- 

 staining protoplasm embedding a nucleus with contained 

 nucleolus. 



Before turning to the further fate of the food, that is to say 

 before considering the process of absorption, it will be well to 

 describe more particularly the contents and characters of the 

 vacuolate cells. 



These when unloaded with nutritive spheres present the 

 appearance shown in fig. 18, where the cell is seen to consist 

 of a thin pellicle of protoplasm surrounding a large central 

 vacuole and embedding a nucleus. The protoplasm stains only 

 slightly. The outline of the cell is exceedingly sharply defined 

 by some staining material which has almost the appearance of a 

 cuticle. The process of loading with nutritive spheres is remark- 

 able, and essentially similar to that described by Miss Green- 

 wood as occurring in Hydra. The protoplasm at one point 

 develops a small vacuole which increases in size, and bulges into 

 the large vacuole. In this the nutritive sphere is formed from 

 the turbid semi-fluid material which first fills it. This process 

 continues until the whole of the cell becomes occupied by small 

 vacuoles, each containing a nutritive sphere. The size of the 

 cell, therefore, does not necessarily vary according to the amount 

 of reserve nutriment it contains. This, however, only holds 

 good for the vacuolate cells of the body. In the blastostyles 

 they are slightly diff'erent. In the first place the large central 

 vacuole is not developed, with the consequence that when the 

 cell discharges its nutritive spheres it frequently shrinks to the 

 condition of a cell with dense, non-vacuolated protoplasm, which 

 stains deeply with picro-carmine. In fig. 22, at 1 is a cell 

 without nutritive spheres, and at 2 one partly filled with 

 vacuoles containing nutritive spheres. 



But the discharge of the nutritive spheres does not always 

 leave the cells smaller and solid. The vacuoles may persist 

 (fig. 22, 4), and the result is a remarkable cell with bubbly 



