PHO TO-MICROGRAPHY 



[CY/. VIII 



specimens will have its own label giving date and method of prepar- 

 ation. It is an advantage to write this label with water- proof car- 

 bon ink, then one can put the label in the dish with the embryos 

 and it will form a part of the picture and serve as a record. 



After the picture is satisfactorily made it is wise to number the 

 embryos on the back of the negative with a wax crayon, and later 

 when the negative is dry number on the front with carbon ink. 

 The embryos are placed in separate bottles each with a copy of the 

 original label and the number corresponding with that put on the 

 negative. This is easily accomplished if the embryos are arranged 

 in definite rows as advised in 281. 



FIG. 169. Camera and special microscope stand for photographing large 

 transparent sections. For this the vertical camera is used (Fig. 161} icith the 

 camera reversed on the sliding frame. This frame is elevated sufficiently to 

 utilize the sky as background and illuminant. The special microscope stand 

 is inclined to the horizontal and placed on the fixed frame supporting the 

 camera; the specimen placed on the stage. For objective one of those objectives 

 shoitn in Figs. 162, 166-168 is used. The objective is screwed into an adapter 

 in place of the ordinary photographic objective. The focusing is performed 

 roughly by the rack and pinion, and then with great exactness with the focus- 

 ing glass. For manipulating the fine adjustment of the special microscope the 

 well known device of a cord over the head of the micrometer screw is used. 

 (See also Fig. /6j.) ( Trans. Amer. Micr. Soc., 



