50 Land and Freshwater Animals 



ADDENDA 



THE progress of technique during the past year has made it desirable 

 to add the following notes. The information they contain is es- 

 sential, and it brings the methods down to date. 



Note i (supplemental to p. 16) — Extensive use of celluloid in the 

 laboratory may be objectionable on account of its inflammability. To 

 avoid fire hazards a so-called "Plastocele" can be used. This product 

 manufactured by the DuPont Viscoloid Company, Arlington, N. J., 

 closely resembles celluloid in appearance and general properties but has 

 great advantage over it in being extremely slow burning and difficult to 

 ignite. For dissolving and cementing plastocele a mixture of equal 

 amounts of methyl acetone and methyl cellosolve is used. 



p. s. G. 



Note 2 (supplemental to p. 26) — The operation of the siphon can 

 be greatly improved by blowing a bulb at the end of the upper arm of 

 it and boring a small hole one-half inch above the tip of the lower arm. 



p. s. G. 



Note 3 (supplemental to p. 26) — -The water is forced by air bubbles 

 into a Wolff bottle which serves to maintain an even flow into the 

 aquarium. The overflow through the automatic siphon is carried into 

 the top of the gravel and sand filter from which it returns to the 

 reservoir. 



p. s. G. 



