414 University of California Publications in Zoology [Vol.19 



appears in the center of both the roof and the floor. Inside the cham- 

 ber around the lower hole was sealed a glass ring which completed a 

 shallow enclosure for water or moist cotton. A heavy steel shank sup- 

 ported the Barber holder. The shank was clamped to a metal base 

 upon which the microscope also was fastened. This sort of moist 

 chamber on a rotary stage has one advantage of much importance for 

 the microdissection of Protozoa : while the animal is being held by 

 water-glass surface tension it may be rotated and so cut through any 

 part at any desired angle. 



The other moist chamber, constructed on a plan very similar to 

 those described by Barber (1914) and Chambers (1915, 1918), was 

 used with a mechanical stage on a Bausch and Lomb binocular micro- 

 scope. The mechanical stage was reversed and fitted onto the left side 

 of the microscope stage, the Barber instrument being attached to the 

 right side. The combined use of the mechanical stage and the Barber 

 holder is often advantageous and sometimes necessary. This arrange- 

 ment just stated, which allows the free use of both hands, has been 

 found very convenient. For a detailed description of the rectangular 

 type of moist chamber, the articles of Barber (1914) and Chambers 

 (1915, 1918) may be consulted, and further account of it here is un- 

 necessary. 



Binocular microscope. — Most of these experiments have been per- 

 formed with the aid of a binocular (Bausch and Lomb) microscope. 

 Especially for microdissection purposes, this instrument is much 

 superior to the monocular microscope. To observe clearly the position 

 and adjustments of the needle in the vertical dimension was found to 

 be very essential in several experiments. As will be described later, 

 all the anal cirri were successfully removed from a few animals without 

 any apparent injury to the body. This, it seems, would have been 

 impossible with only monocular vision. Furthermore, the general con- 

 tour of the organism, the relative positions and movements of its 

 organelles, the cyclosis of the granules of the endoplasm, the contrac- 

 tions of its vacuole and its forms of behavior in creeping and swimming 

 arc much more satisfactorily studied under the binocular microscope. 

 The use of both eyes soon becomes fully as desirable in microscopical 

 as it is in unaided vision. 



Glass needles. — Much of one's success or failure in microdissection 

 can be attributed to the quality, shape and size of the needles employed. 

 Soft glass needles are of little value in making incisions, but because 

 of their flexibility they may be used to hold the protozoan without 



