and Laboratory Methods. 



1570 



first grade of the high school. The objects studied are ahnost exclusively 

 arthropods and vertebrates, and the M'ork is planned for laboratories not equipped 

 with microscopes. The comparative method is well sustained throughout the 

 book, and the manner of presentation is one well adapted to cultivate independ- 

 ence in the pupil, and to develop the scientific method. The efi^ort to combine 

 both text-book and laboratory guide in two hundred pages has been less suc- 

 cessful, and the reputed micro-photographs which are offered as substitutes for 

 the compound microscope will be of little value even to schools with meager 

 equipment. c. a. k. 



Peters, A. W. Some Methods for Use in the 

 Study of Infusoria. Am. Naturalist, 35 : 

 553-559. I90'- 



The Yarn Siphon is used for separating 

 Infusoria in large numbers from both 

 the culture water and the solid debris 

 which it contains. Transfer the liquid containing the Infusoria from the culture 

 jar to a Stender dish, and mix thoroughly to obtain a uniform distribution of the 

 organisms. Next, several pieces of woolen yarn are laid side by side without 

 twisting, moistened, and placed with one end in the Stender dish and the other 

 hanging down the side of the dish, and siphoning into a collecting vessel. The 

 yarn filters the water so that only active organisms pass over into the lower 

 vessel. 



The Tube Filter is an apparatus for concentrating the Ciliata contained in 

 a large amount of water, and changing the culture medium. The ordinary 

 methods of filtration fail in this case because so many organisms stick to the 

 filter paper. The tube filter is a piece of large glass tubing, over one end of 

 which filter paper is fastened with a rubber band. This tube is lowered into 

 the culture vessel, and the filtration takes place upward. More culture fluid, or 

 any desired solution, may be added to the outer vessel from time to time, and 

 the filtered water removed from the tube by means of a siphon with its lower 

 end bent up to prevent it running empty. 



The U-Cell (Fig. 1) is also a device for filtration, but on a 

 smaller scale. It admits of microscopical observation. It con- 

 sists of a long U of large, close fibered darning cotton, which 

 has been previously moistened and placed between two thin 

 slides. The cotton is so placed that the U is two-thirds the 

 length of the slide, and that its ends barely project beyond the 

 parallel ends of the slides, which are held together with rubber 

 bands. If it is desired to examine with a higher power of the 

 microscope, a cover-glass may be substituted for one of the 

 slides, but in this case narrow strips of slides should be laid 

 over the cover-glass where the rubbers go around it. The cot- 

 ton yarn should be of such a thickness that the slides will be 

 0.5 mm. apart when the cell is complete. To fill the cell it 

 should be held nearly vertical, and the culture fluid and In- 

 fusoriaWnserted through the open end of the U with a small 

 pipette. Part of the water will flow out through the cotton, but part will be 

 retained by capillary attraction. By repeated use of the pipette any desirable 



Fig. 1. 



