Photography — Its History, Position, and Prospects. 153 



tion of second sporangium. 8. Infusorioid spore highly mag- 

 nified. 4. Do. do. in germination. 5. Oogonia in various 

 stages, magnified. 6. Portion of wall to show the apertures. 



7. Sa/prolegnia monoica. — Oogonium with antheridia, one 

 of which has penetrated the cavity by means of a rootlike 

 process. 



8,9. Saprolegnia dioica. — 8. Thread magnified, producing 

 sperrnatozoids. 9. Spermatozoid highly magnified, killed with 

 iodine. 



10 — 12. Achlya prolifera. — 10. Tip of thread, showing the 

 infusorioid spores making their way to the tip of sporangium, 

 and new sporangium formed at the base. 11. Infusorioid spores 

 surrounded by membrane, and two empty cases, highly mag- 

 nified. 12. Perfect spores free, highly magnified. 



13, 14. Achlya dioica. — 13. Tip of thread containing an- 

 theridia, from some of which the sperrnatozoids are escaping. 

 14. Sperrnatozoids, killed with iodine, highly magnified. 



14* — 16. Pythvmn monosjpermum. — 14.* Thread with 

 sporangia magnified. 15. Infusorioid spores collected at tip 

 of a sporangium, highly magnified. 16. Oogonium with an- 

 theridium. 



17 — 20. Aphanomyces stellatus. — 17. Thread showing the 

 spores making their way, one by one, to the tip. 18. Spores 

 surrounded by membrane and empty cases. 19. Do. free. 

 20. Oogonia with antheridia. 



The figures are all borrowed, with a single exception, from 

 the above-mentioned memoirs. 



PHOTOGRAPHY— ITS HISTORY, POSITION, AND 

 PROSPECTS. 



PART I.— HISTOKY OF PHOTOGRAPHY, f 

 BY J. W. M f GAULEY. 



In treating of a science which, although the creation of but 

 a comparatively recent period, has become so extensive as to 

 be dependent on an immense number of principles, to include 

 a great variety of processes, and to be scattered over a vast 

 body of literature in every modern language, it will be im- 

 possible, even in a paper of unusual dimensions, to give more 

 than a glance at its past history, its present position, and its 

 future prospects. It is not our object to teach the Art of 

 Photography, we propose merely to trace its progress from its 

 first glimmerings to its now wondrous development ; to give a 



f The remaining parts will follow at early dates. 



