LIFE HISTORY OF TWO RARE CILIATES 367 



As a result of these observations he considered Actinobolus 

 an holophytic form. 



Entz noted a difference between the nuclei found in old and 

 young cells; the nucleus of the former he described as an elon- 

 gated, cord-like organ, frequently broken up into spherical 

 segments, presenting the appearance of a mass of free nuclei; 

 the nucleus of the latter, a kidney-shaped, horse-shoe form or 

 spherical mass of chromatin. He found, scattered among the 

 filaments of the algae, many thin-walled cysts, within which 

 two, infrequently four, distinct masses of protoplasm were seen 

 rotating; He interpreted the cysts as division or reproductive 

 cysts; the protoplasmic masses as daughter cells. At the time 

 of encystment the following changes occurred: The organism 

 withdrew its tentacles, lost its cilia, the protoplasm became 

 very dense, the nucleus shortened and division of the cell fol- 

 lowed. After fission the new individuals emerged from the 

 cyst, taking on within a short period of time, the form of the 

 mature cell, developing tentacles and cilia, the protoplasm again 

 showing the characteristic foamy structure and the nucleus 

 elongating to form the cord-like organ typical of the adult cell. 



Von Erlanger, working at Heidelberg under Biitschli, was the 

 next contributor to our knowledge of this ciliate, making a special 

 study of the structure and function of the tentacles. He found 

 these organs regularly arranged in the ciliary grooves extending 

 from anterior to posterior end of the body and could trace them 

 inside of the body in their contracted state, although he states 

 in a foot note that Biitschli was unable to confirm his observation 

 in this particular. In a fully extended tentacle, von Erlanger 

 distinguishes three regions; the proximal part, thick and spher- 

 ical in form, a long slender portion (both of these parts being 

 perfectly transparent) ; and a slender opaque rod terminated 

 by a small knob much more minute than the similar structure 

 found in the suctorian tentacle. Fully retracted tentacles 

 formed a peripheral row of minute rods appearing like tricbo- 

 cysts found in other ciliates. Tentacles treated with osmic 

 acid showed an extremely fine dart projecting bej^ond the knob. 

 Like Entz, von Erlanger never saw the tentacles used to seize 



