CH. X] 



SERIAL SECTIONING 



474. Numbering the Serial slides. For temporary num- 

 bering a fine pen with Higgins' waterproof carbon ink serves well. 

 If the slide is clean one can write on it as well as on paper. When 

 the ink is dry it should be coated with thin shellac or with thin 

 xylene balsam. Sometimes thin collodion is used. It is also im- 

 portant to write the number of the slide with a writing diamond. 

 The double marking is desirable because with wet slides the dia- 

 mond number is hard to see, while the ink marks are clearly visible. 

 One is not so liable to wipe off the sections if the ink mark is 

 present. 



FIG. 254. Egg pipette. This is made by putting a short piece of soft rubber 

 tubing over the end of a glass pipette with rubber bulb. With this one can 

 handle the eggs both fresh and hardened without any danger of injury. (Jour. 

 Appl. Micr. 1898, p. 720. ) 



FIG. 255. Lens holder. A 

 lens in such a holder is very 

 convenient for sorting and 

 orienting small eggs or em- 

 bryos in imbedding. One can 

 ha ve the eggs in a watch-glass 

 of melted paraffin on a copper 

 warming plate (Fig. 241} and 

 arrange the eggs or embryos 

 under a lens in such a lens 

 holder. Then if cold water is 

 poured on the plate around the 

 -watch-glass the paraffin will 

 cool and hold them in place. 

 (Cut loaned by the Bausch & Lomb Opt. Co.) 



FIXING AND STAINING FOR SERIES 



475. Fixing. The two most used fixers for embryos are 

 Zenker's fluid and Formaldehyde ( 406, 429). For those unskilled 

 in microscopic technic, or for one who is exceedingly busy the best 

 results are obtained by putting the embryos in formaldehyde, (10 

 parts of formalin, the formalin of the pharmacy, and 90 parts water 

 answers well). If there is plenty of this the embryos are likely to 



