52 THE MICROSCOPE. April 
The Hydroids. 
By H. J. CLEMENTS, 
CHEYENNE, WYO. 
As the summer approaches, many of those interested 
in microscopy will doubtless be among the favored, who 
can spend a part of their vacation at the seaside, and as 
one of the easiest obtained and most interesting of the 
forms among the multiplicity of life there, are the 
Hydroidea, perhaps a few notes upon them and on some 
methods of study will not be amiss. 
A number of species are to be found on the Fucus or 
Bladder-wrack which has been stranded at low water. 
By looking over a number of bunches of this. one can 
hardly fail to find patches of white or pinkish animal- 
like material, and if he places these into the water for a 
moment, he will be rewarded by seeing the many ten- 
tacles expand and the beautiful zoophytes resume their 
accustomed activity. 
Other species will be found attached to piers, within 
easy reach at low water, still others will be found grow- 
ing to the rocks in the tide-pools. 
If the collected hydroids are placed in pails or bottles 
with clean salt water, taken home and transferred to 
dessert dishes in which fresh sea water is placed and oc- 
casionally changed, the student will have aquaria that 
will easily interest and instruct him for hours at a time. 
Care must be taken not to crowd these dishes with too 
many colonies. 
A little observation will make it evident that these re- 
markable creatures are apparently of three classes, one 
often having the appearance of that shown in figure 1, 
and known to zoologists as the Tubularian Hydroids. 
These are essentially tubes closed at one end, an opening 
for the injestion of food being at the other end, which is 
thus spoken of as the mouth. This end is also enlarged 
