ACID PHOSPHATASE ACTIVITY AND ULTRASTRUCTURE OF AGED CELLS OF EUGLENA GRANULATA1,2

Ultrastructure and acid phosphatase activity of aged calls of Euglena granulata are reported. Cells are spherical, quiescent, and nonflagellated. The most conspicuous attribute of aged cells is the accumulation of cyloplasmic vacuoles and lysosome-like structures containing heavily stained, pigmented bodies and membrane fragments. In chloroplasts, portions of whorled lamellae arc abscised and subsequently incorporated into lysosome-like structures; osmiophilic granules increase in number. Membranes surrounding eyespot granules disappear and the granules themselves become diffuse; the usual association with microtubules is not seen in aged cells. Acid phosphatase precipitation accumulates largely at the maturing face of dictyosomes and associated vesicles; there is also activity in multivesicular and lysosome-like vacuoles.