162 APPENDIX (PART II) 



Dendrocometes, a remarkable acinetarian, is nearly always to be found on the gill, 

 plates of the water shrimp Gammarus. 



Stentor, according to our experience, is generally to be found in pools on a stiff 

 clay, rather than in sandy or chalky districts. 



In all cases the secret of keeping these animals is to use small glasses, to 

 avoid evaporation, and to partly change the water by means of a clean 

 pipette every day. The temperature of the room where the aquaria are, 

 should be as equable as possible. 



The student will soon learn that the succession of protozoa in large aquaria, 

 following as yet unknown laws, is one of the most puzzling facts about 

 these animals. One day the tank will be swarming with, say, Actino- 

 sphaerium, and in two days they may have all disappeared. See page 15. 



CHAPTER XXIV. 



In taking nature photographs, the conditions are so various that the photographer 

 will require apparatus to suit special cases. He can, of course, provide him- 

 self with a number of cameras, but the young nature student can hardly be 

 expected to do -this. An attempt has been made to design a camera which, 

 while useful for all ordinary kinds of work, has yet special possibilities. 

 In photographing live animals, particularly those which are small and have 

 to be taken at close quarters, the nature photographer will at once feel the 

 necessity of some means by which he can follow the slightest movement of 

 the creature with his eye and with the focussing screw, while at the same 

 time he has the power of exposing his plate on the instant. In the camera 

 shown in the illustration, which is of half-plate size, this power is given by 

 the attachment, when necessary, to its left side, of a light quarter-plate 

 camera, of which the lens has exactly the same focus as that of the first. 

 The idea is, that in an ordinary half-plate photograph of an animal the 

 latter will seldom occupy more space in the centre than would be covered 

 by a quarter-plate. In practice, the dark slide or magazine is placed in 

 position at the back of the main camera and the slide drawn ready for 

 exposure. The object is focussed upon the ground glass of the supple- 



