26 THE AMERICAN MONTHLY [January, 



Similarly distilled water may be at once substituted for osmic 

 acid solution, or i per cent, chromic acid or other fluid that 

 does not differ at all widely from water in specific gravity. But 

 with certain fluids the gradual substitution is necessary, and it is 

 above all necessary in replacing water on a watery solution by 

 alcohol, and this, in the case of large specimens intended for 

 museum purposes as well as smaller objects, can very con- 

 veniently be carried out by the simple apparatus I have described 

 above. 



Another method of eftecting this substitution is the one devised 

 by Schultze ; and this seems to possess some decided advantages, 

 at least for small objects. Schultze places the objects which he 

 wishes to transfer from water to alcohol in a tube full of water, 

 plugged at one end, and closed at the other by a diaphragm of 

 chamois skin. The tube is placed in a vessel of alcohol and 

 left there until by a process of diftusion through the diaphragm 

 the water in the tube becomes completely replaced by alcohol, 

 the same material being used for the diaphragm. The time 

 which will be occupied before complete substitution takes place 

 will vary with the capacity of the tube and the diameter of its 

 orifice ; and a series of experiments and calculations would have 

 to be made before this metliod could be used with the assurance 

 of good results. Should it be desired to have the specimens in 

 absolute alcohol at the end of the process, some calcined sulphate 

 of copper may be placed in the outer vessel." 



BIOLOGICAL NOTES. 



A ^A^ater-bug — Our friend Zabriskie of the New York Micro- 

 scopical Society found a water-bug in the waterworks of Flatbush 

 which has been named by Bergroth of Finland Rhejiniatobates 

 rileyi. It has also been found along the C. and O. canal above 

 Washington. Figures and descriptions are to be found in Insect 

 Life for January. This periodical can be obtained by entomolo- 

 gists by addressing Division of Entomology, Agricultural Depart- 

 ment, Washington. D. C. 



The insect is shy and hard to capture, which accounts for its 

 tardy appearance in museums. It seems to prefer the vicinity of 

 rocks and rocky beds. Specimens in various stages of develop- 

 ment were taken in June. 



Potato Scab. — Prof. H. L. Bolley announces that this disease 

 of the potato-tuber can now be kept under entire control at very 

 slight expense. Full details are given in a bulletin of the North 

 Dakota experiment station. The ravages of the disease have 

 come to be very serious, the losses averaging one-half pound per 

 hill and often amounting to more than that figure. The disease 

 attacks not only the tubers, but the base of the vines, resulting in 



