418 University of California Publications in Zoology [Vol.19 



for microdissection studies. Plate 29, fig. 1. illustrates several struc- 

 tures which are very favorable for operative work on the neuromotor 

 apparatus. The large C-shaped nucleus permits the cutting of the anal 

 cirri at several points with no injury to the nucleus. Also, the cyto- 

 stomal fiber may be cut at various angles and the motorium destroyed 

 likewise without injuring the nucleus. The stiff, fairly tough pellicle 

 which envelops the body ably maintains the normal form after an 

 incision, often very deep, has been made. The remarkable firmness of 

 this structure makes possible the removal of cirri with no apparent 

 injury to the body. The projection of the oral lip and of several cirri 

 affords successful excision of these parts, and the definite grouping of 

 the frontal, ventral, anal, and marginal cirri permits various transec- 

 tions and combinations of transections and excisions that have proven 

 to be exceedingly useful in studying the functions of these groups of 

 organelles in creeping and swimming movements. The location of the 

 single micronucleus at the anterior end of the body is especially favor- 

 able for ascertaining more accurately the specific role of this interest- 

 ing and important organ. 



THE LIVING ORGANISM 



Owing to the invaluable aid of water-glass surface tension for the 

 control of Protozoa in a hanging drop, it is now possible to study 

 active, living organisms in minute detail under the highest magnifica- 

 tion. With a properly constructed moist chamber, the time limit for 

 this study depends rather upon the endurance of the observer. A 

 living Euplotes was held continuously within the field of a 2 mm. Zeiss 

 apoehromat lens for more than two hours, at the end of which time. 

 when a drop of water was added, the animal swam slowly about ; 

 within half an hour its movements were apparently normal. This 

 allotment of time is ample for a complete, detailed review of all the 

 structures and movements of the organism that may appear within the 

 range of microscopical vision. By properly adjusted, transmitted light, 

 the binocular microscope with an apoehromat lens affords here the view 

 of a living, active form that rivals any of nature's finest displays. The 

 study of living organisms always lends increased interest and adds the 

 essential complement to our knowledge of the structures and relations 

 disclosed in fixed material. 



