WATER-MITES AND THE WATER-BEAR. 261 



occupying much of the upper surface, and so arranged 

 and shaped that they leave between them, in the mid- 

 dle line of the body, a V-shaped space which may be 

 white, yellow, or other color. These spots are called 

 cceca or the coecal markings, the word being the plural 

 of coecum, meaning a certain part of the lower intes- 

 tinal canal. They are useful to the student in identi- 

 fying the species. 



The lower or ventral surface is the most important 

 part to the observer who desires to ascertain the name 

 of his specimen, or to the stu.dent who wishes to make 

 a moire serious study of the animals, for on this surface 

 are the parts most used by the naturalist in classifying 

 the mites. The observer must therefore seek to have 

 the little creature arranged on its back before it is 

 placed under the microscope, so that the ventral sur- 

 face shall be presented to the objective. As this is 

 sometimes a difificult operation to accomplish without 

 injuring the delicate body, the writer has used for the 

 purpose a little home-made contrivance that answers 

 well and can be made by any one. A hole about half 

 an inch in diameter is drilled through a glass slip, and 

 into one side is cemented with shellac a thin-glass 

 circular cover a little smaller than the hole, so that 

 the cover may not be flush with the surface of 

 the slip. It is not difificult to grind a hole through a 

 thin glass slip if the file or other grinding tool is kept 

 wet with turpentine. The aperture may not be a per- 

 fect circle ; it will probably lie very irregular — I know 

 mine 'is — but it will answer every purpose. The mite 

 is placed in this cell, and a thin cover applied to the 

 opposite side, thus forming a glass box that can be 

 turned over for the examination- of both surfaces of 



