258 



Transactions of the Society. 



who has devoted much attention to the artificial fertilization of the 

 eggs of HcJdnus. 



The photomicrographs of maiine parasitic Protozoa I need not 

 describe, as explanatory titles are attached, and I think the same 

 may be said to apply to most of the other photographs exhibited 

 to-night ; therefore I may pass at once to some lirief description of 

 how they were obtained. 



I began taking my first photographs of marine animals and 

 their anatomy at the time that my dear father, the late Dr. P. 

 Martin Duncan, occupied the Presidential chair of this Society, and 

 these early attempts were undertaken with a view to relieving him 



Fig. 13. — Stereo-binocular Microscope and Verascope Camera 

 in position for taking Stereoscopic Photomicrographs. 



from some of the long hours of eye-strain in the course of his 

 microscopic investigations into the anatomy of the Corals and 

 Echinoderms. Those first studies were obtained with the aid of an 

 old wet-plate camera and collodion wet-plates of home manufac- 

 ture, which gave me a very useful insight into the chemistry of 

 pliotography. I have found that for practically all marine 

 biological work either an isochromatic or a panchromatic plate 

 must be used to obtain the best results, and most truthful render- 

 ing into monochrome of the various colour-values of the subject. 

 Subsequent enlargement of part or tlie whole of the negative often 

 being necessary, it is most important to select a plate of fine grain. 

 Most of the direct prints and enlargements exhibited to-night 



