INTRODUCTION. 5 



may be obtained from dealers * at a cost not exceeding 

 sixty cents per student. Orders for these should be 

 placed in the early summer, so that no difficulty or delay 

 may occur later. Much of the other material may be 

 obtained when wanted, but such as cannot be had in 

 the colder months frogs, tadpoles, snakes, turtles, 

 crayfish, insects, earthworms, etc. should be collected 

 in the summer and preserved in alcohol or formol for 

 use later. Those which require injection should be so 

 prepared before being placed in the preservative fluid. 

 Alcohol.- -The most important of all reagents. It can 

 be purchased, tax-free, by incorporated institutions of 

 learning upon the fulfilment of certain conditions, which 

 may be learned by application to the Collector of Internal 

 Revenue in the district in which the institution is situated. 

 As it comes from the distiller it is usually about 95% 

 alcohol, the rest being water. This is too strong for 

 most purposes, and for the preservation of material it 

 should be reduced to 70% by the addition of Avater. 

 A convenient method of making different strengths of 

 alcohol is as follows: First, with an alcoholometer, find 

 the percentage of alcohol in the supply. Then fill a 

 metric graduate with alcohol to the mark which corre- 

 sponds to the desired per cent, and then add water until 

 the mixture reaches the mark corresponding to the per 

 cent, with which you started. Thus to make 70% from 

 94% measure out 70 cc of alcohol, then add water until 



* Supply Department, Marine Biological Laboratory, Wood's 

 Hole, Mass; Dr. F. D. Lambert, Tufts College, Massachusetts; 

 H. H. and C. S. Brimley, Raleigh, N. C.; Supply Department Hop- 

 kins Laboratory, Stanford University, California. Skeletons and 

 rarer forms can be obtained from H. A. Ward, Rochester, X. Y. ; 

 Kny-Shearer Co., 225 Fourth Avenue, New York. 



