PROCEEDINGS OF THE SOCIETY. 225 



h;mdy size. For higher power microscopy the speaker modified the 

 Rousselet live-box by having a thin ring of metal put into it, to the 

 underside of which was cemented a very thin cover-glass. This device 

 made it quite possible to focus a T V immersion objective upon details in 

 the median plane of a fair sized Daphnia. The Rousselet live-box was 

 preferable to a compressor, since the lid could be moved in two planes 

 and so controlled the position of the objects. For certain purposes he 

 attached the animals to the end of a very fine wire with a minute drop 

 of sealing-wax or shellac varnish. If carefully done without entangling 

 the antennas all the movements of the creature could be performed in a 

 perfectly natural manner, and yet it could not escape from the field of 

 vision — points of the utmost importance when investigating the currents 

 produced by the antennas, etc. 



He wished to insist very strongly that these small aquatic animals 

 should lie studied under natural conditions, and for this purpose he sug- 

 gested a large observation tank sunk into the ground with a passage-way 

 all round it, and hoped that some day this might be arranged. For the 

 preservation of specimens he usually employed formalin — spirit was 

 also good, but not so generally useful ; spirit and glycerin, or formalin, 

 spirit and glycerin together were also useful compounds. 



His specimens were stored in tubes about 1^ in. by f in., packed in 

 boxes or drawers between strips of cardboard arranged to form a series 

 of divisions as in an egg-box, and seldom mounted on slides. 



The President congratulated not only Mr. Scourfield, but the 

 Society on the extremely practical manner in which the subject had 

 been put before them. It was the exposition of a man of experience, 

 and Mr Scourfield had explained just those things which were essential 

 for working purposes. 



Mr. E. J. Spitta was interested in Mr. Scourfleld's method of re- 

 structing the movements of animals such as the water-flea, as he had 

 experienced much difficulty in keeping them continuously in the field 

 of view. When preparing kinematograph films of pond-life, his own 

 plan was to make a series of vulcanite cells of different depths varying 

 from a fiftieth to a hundredth of an inch, and to suit the depth of the 

 cell employed to the thickness of the object — a matter of trial and 

 error, for the cover-glass must be just heavy enough to press upon the 

 object lightly and yet firmly, but not too heavily, or the animal would be 

 killed. To make these cells of different depth, he stuck a few on to 

 ordinary micro-slips, and filed them down with a broad fine flat file ; a 

 coarse file tore the vulcanite and the scratches prevented the cover-glass 

 fitting closely. 



Mr. Scourfield said that the question of holding Entomostraca under 

 water was one of considerable difficulty. The varnish he used set very 

 well in water, and held Daphnia for a considerable time, but would not 

 hold a Cyclops for more than two or three minutes. He would like to 

 hear of a suitable cement for the purpose. 



Mr. Spitta said he had secured on his film a peculiarly jerky Cyclops, 

 and thought perhaps the animal waited before making one of those 

 violent jumps until the coast was clear of all obstructions, since he had 

 no record of any one Cyclops colliding with another. 



