COLLECTING AND MOUNTING ROTIFERA. 325 



nicely and fully extended. Being then sure that those remaining 

 were sufficiently narcotised, they were killed in the same way, 

 and each, when fixed, was immediately removed with a pipette 

 into 2J per cent, formalin and then transferred again through 

 several changes of the formalin solution so as to get rid of all 

 trace of osmic acid. Finally the specimen was transferred to a 

 cavity slide, covered and finished in my usual way. 



In preparing non- free -swimmers I was greatly assisted by 

 Mr. Traviss's cutting and holding scissors,* by means of which a 

 small bit of pond weed to which the animal is fixed or attached 

 can be cut and transferred at pleasure. 



In later times I have ringed my slides first of all with a very 

 thin ring of picture copal varnish followed by a coat of Japan 

 gold size, and then with several coats of Heath's cement (gold 

 size-shellac-indiarubber), finally finishing with three more coats 

 of gold size. Several persons beside Mr. Heath have produced 

 a micro-cement containing gold size and pure rubber, and 

 with the assistance of Mr. Waddington I have myself com- 

 pounded one containing pure caoutchouc dissolved in mineral 

 naphtha and mixed with gold size and Canada balsam. This 

 appears to answer very well, and to be a solution of a 

 problem which has puzzled microscopists for many years. 

 Messrs. Clarke & Page seem to have produced a cement wath 

 similar ingredients and properties, and Flatters & Garnett have 

 also done the same under the name " Brown Kinging Cement," 

 the actual composition of which is kept secret, but, I take it, it 

 contains a small proportion of indiarubber, which appears to be 

 essential. I hope that Mr. Heath will get a reputable gold size and 



* Traviss's cutting and holding scissors were first made by him 

 on the principle of a grape scissors which holds the grape that is being 

 cut off. More recently I advised Mr. Traviss to have his scissors 

 plated or made of nickel silver to prevent the blades rusting, and also 

 to have the handles made a little longer, say 4^ to 6 inches long, to 

 enable me to cut off a piece of weed with the animals attached thereto 

 under water in my window aquarium, to be then transferred to the 

 solid watch-glass, micro-trough, etc. 



