THE HYDRA. 



A tiny green or light brown jellv-like lump aa large as the head 

 of a small pin ; a slender stem, perhaps one fourth of an inch long, 

 with seTeral transparent threads waving from its tip ; or a graoef a 1 

 vase with a few blnnt projections from the top ; any or all of these 

 alingiug to water-plants or any other support in fresh-water ponds 

 or quiet streams, may be the hydra we are seeking. We tell the 

 children we are going to look for a new animal, and invite some of 

 the older ones to join ns in a walk, thus enlisting their interest in the 

 hydra in advance. It is a wise precaution to fill our glass jars at 

 several different ponds, rather than to fill several jars from one 

 pond, because the fact that hydras have been found in a given 

 place one year seems to be no guarantee whatever that they will be 

 found there the next year. After the water has settled, the hydras 

 will expand and many of them will collect on the sides of the jar. 

 A dozen watoh-orystals filled with pond-water, each with a bit of 

 duckweed or some other green water-plant, make excellent ponds for 

 as many hydras, in which children can examine them with magni- 

 fiers, watch them eat, and observe the di£Eerent shapes they assume. 

 Pupils that are old enough will eojoy making a series of drawings 

 showing these different f aram. 



Four questions may be put upon the blackboard, one at 

 a time, for the children to answer from their own ob- 

 servations : What is a hydra ? Where does it live ? 

 What can it do ? How do new hydras grow ? 



After a few days the answers to these questions will 

 bring out many of the following facts, in addition to those 

 already mentioned. 



The hydra is a green or brown tube, attached by its 

 lower end to some support, and sending out several ten- 

 tacles near its upper end. Fig. 1 shows one magnified 

 many times, hanging mouth downward, from a bit of 

 wood. The upper end of the tube beyond the tentacles 

 is called the proboscis. At the end of the proboscis is 



