162 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



Subsurface water: Golden Gardens City Park, Seattle, Washington, lat. 47°43' 

 N., long. 121°24' W., 1,000 cc, from muddy sand with scattered stones, February 

 4, 1958. 



The use of lactic acid in copepodological workfhas already been 

 mentioned briefly (Gooding, 1957). This fluid is particularly suitable 

 as a temporary mountant for small arthropods since it is directly 

 miscible with most general preservatives, penetrates rapidly, clears 

 satisfactorily, evaporates slowly, and has a low refractive index. It 

 also renders specimens supple, so that dissection is facilitated. How- 

 ever, since it macerates the soft parts of the body, it cannot be used 

 when the animals are required for study of the internal anatomy. 

 The following procedure has proved very useful and should be appli- 

 cable to small Crustacea other than copepods. 



A coverslip of sufficient size is fastened over the hole in a Bio-Plastic 

 Micromount Holder (Ward's Natural Science Establishment, Inc., 

 Rochester, N.Y.) . Since this hole perforates the plastic slide, the two 

 parts together form essentially a deep-well slide. The use of modelling 

 clay for attaching the coverslip allows the latter to be removed easily 

 whenever necessary. The specimen is then mounted in a small drop 

 of lactic acid at the bottom of the "well" (i.e., centrally on the face of 

 the coverslip nearest the slide) . Staining is usually unnecessary and 

 often undesirable but, if required, a weak solution of methyl blue in 

 lactic acid may be used as the mountant. 



When observations and drawings are being made, the slide should be 

 placed coverslip uppermost so that the specimen is protected in a 

 hanging drop within the cavity. If a coverslip of sufficient thinness 

 is used initially, even an oil-immersion objective can be employed for 

 examination, although, of course, some resolution is lost since the 

 condenser cannot be oiled. The reverse position of the slide allows 

 dissection and rearrangement of the animal or its appendages to be 

 made with ease on the stage of a dissecting microscope. Any append- 

 age which cannot be manipulated so as to show the relation of its parts 

 satisfactorily can be removed to a standard microscope slide and 

 flattened partially in a drop of lactic acid under a coverslip. Movement 

 of the latter will usually produce the desired position (see the figures 

 of "flattened" appendages included below, e.g., 5d). 



Such temporary mounts will remain in good condition for long 

 periods if protected from dust and if the lactic acid is renewed occa- 

 sionally. Hoyer's mediimi (see Baker and Wharton, 1952, pp. 10-11, 

 for formula) has proved satisfactory as a permanent mountant since 

 specimens can be transferred to it directly from lactic acid. 



A camera lucida was used in making all drawings. This device also 

 permitted a simple and accurate method for comparing a series of 

 specimens of one species. Drawings of the copepod first examined 



