250 PHOTOMICROGRAPHY 



be used, but the vertical arrangement has several points 

 in its favour ; the object can be readily laid on a table 

 below it, and the camera can so easily be carried into the 

 best position for daylight. Colour photography is fre- 

 quently of great value, and stereoscopic photomicro- 

 graphy finds its greatest application in this field. Plates 

 3 and 27 are examples. 



Objects in Preservative Fluid, Dissections, etc. (Plates 

 2. A and 26. B). Specimens preserved in bottles should 

 be removed when possible and immersed in a dish of the 

 preservative fluid or water for photography. Immersion 

 in a liquid has the effect of considerably increasing the 

 apparent depth of focus of the objective, and greatly 

 improves the appearance of many specimens by sup- 

 porting hairs, tentacles, and the like. Tremors on the 

 surface of the liquid must be carefully guarded against. 

 A vertical camera as illustrated at Fig. 42 is the most 

 convenient to use under these conditions. 



The Chick in Egg (Plate 2.A), and the Spider (Plate 

 26. B), were immersed in water and spirit respectively, a 

 piece of black paper, previously soaked in spirit to prevent 

 the formation of air bubbles on its surface, being laid 

 on the bottom of the dish to form a suitable background. 

 Plasticine can be used to support the object firmly. 

 Specimens that cannot be laid in a dish or supported 

 therein may be suspended in a flat-sided trough, the most 

 convenient arrangement when a vertical camera is not 

 available. 



The precautions against reflections, detailed in the 

 section on culture tubes, must be observed when photo- 

 graphing delicate specimens that cannot be removed 

 from the jar in which they are preserved. 



Dry Specimens (Plates 26. A and 4. A). The advantage 

 of immersion in liquid was referred to in the last para- 

 graph, but immersion is not always applicable or desir- 

 able, and in such cases some simple device must be 



