LIFE HISTORY OF TWO RARE CILIATES 357 



in various stages of digestion. In many of the total prepar- 

 ations the body of Colpidium is seen practically intact (figs. 

 23 and 25) while in others the cytoplasmic envelope has disap- 

 peared, leaving the macronucleus, with the micronucleus lying 

 in a depression on its sm-face, surrounded by the endoplasm 

 of Spathidium (fig. 30). Other deeply staining bodies, varying 

 greatly in size and number, are scattered throughout the pro- 

 toplasm. Doubtless they are the remains of food particles 

 which have been subjected during a longer period of time to 

 the action of the digestive ferments. According to Calkins, 

 the more conspicuous granules found in the protozoan cell are 

 formed by the breaking down of the food particles, some of 

 which are directly assimilated while others remain as reserve 

 nutriment. He notes the difference in appearance of the pro- 

 toplasm of a well-fed and a starved Paramoecium; that of the 

 former showing a typical granular structure, that of the latter, 

 the entire absence of granules. This contrast is very marked 

 in Spathidium, the protoplasm of a well-nourished individual 

 being densely granular, that of the starved forms appearing as 

 a clear and almost structureless substance. 



At the posterior end of the body is a large single terminal 

 vacuole which, at room temperature, pulsates on an average 

 of once a minute. Miiller describes two vacuoles in Enchelys 

 spathula, one near the middle of the body, the other at the pos- 

 terior end. In the species under observation, two vacuoles 

 are sometimes seen for a time at the posterior end, but sooner 

 or later the two coalesce in one large terminal vacuole (fig. 27). 

 At the systole the contents of the vacuole are expelled through 

 a minute opening at the extreme tip of the body. 



.Although total preparations and sections of vegetative cells 

 as well as early and later division stages have 'been carefully 

 studied, the observations have yielded no positive evidence of 

 a differentiation of the nuclear material into two structures, a 

 micronucleus and a macronucleus. In a few instances, vesicular 

 bodies, varying from spherical to retort-shape containing deeply 

 staining granules, have been observed (figs. 10 and 14). The 

 contained granules are elongated and constricted at the center 



