56 THE MICROSCOPE. Apr i) 
study, but rarely will they be, when thus killed, ex- 
panded; for they are exceedingly quick to move when dis- 
turbed. By boiling the fluids and quickly dropping in 
the colonies, fairly good results are possible, but in time 
the tissues tend to break down, so it cannot be relied on 
for indefinite preservation. 
The best method of all, when the only object is to kill 
the colonies with hydranths naturally extended, is to 
slowly add crystals of epsom salts tu the water in which 
they are living. It is best to take small colonies in a 
watch glass for this. The salt narcotizes them, and if 
they are then placed in a 5 per cent solution of formalin, 
they make beautiful specimens, especially if stained with 
an aqueous stain and mounted in glycerine jelly. 
The sertularian and planularian hydroids (fig. 7), 
are generally classed with the preceding group, but as 
they will strike the beginner as being so distinctive, I 
briefly speak of them here. Like the Campanularia they 
are covered with a case, which here reaches its highest 
development, and with it the zooids are the most nervous. 
They are easily recognized as those delicate, white, wiry 
masses sometimes mistaken for sea-weed. They are 
usually found in great abundance on the Fucus between 
tide-marks. In the early summer, the egg-cases form a 
very prominent feature. It is extremely difficult to kill 
them expanded, but the last method suggested, will often 
succeed in giving beautiful specimens. 
Iowa Plants.—Professor L. H. Pammel has distributed 
his first fascile of Iowa Plants. The others will be dis- 
tributed as soon as the material is ready. 
Diseased Pork.—A French periodical reports fifty peo- 
ple killed in an epidemic from eating pork affected by the 
specific bacillus of the pneumo-enteritis of pigs. Hog 
cholera had prevailed : One man had sold fifty-seven pigs 
of which forty-one had died of the disease. 
