APPENDIX 149 



few days hydra, if present, will be found on the side of the 

 jar toward the light. In the autumn secure leaves from 

 the bottom of the pond and some of the surface mud. 



Hydra will nourish if the jar is kept supplied with an 

 abundance of "water-fleas," Daphnia, Cyclops, Cypris, 

 etc., and budding will be abundant on the hydras. If the 

 food supply is allowed to diminish reproductive organs will 

 often begin to appear. 



To kill hydra expanded remove a single specimen from 

 the aquarium with a pipette and place in a perfectly clean 

 watch glass with only a small amount of water. When the 

 animal in the watch glass is well expanded dash hot Wor- 

 cester's fluid, or hot Bouin's fluid, over it and allow to stand 

 ten minutes. The animal may then be washed and treated 

 for further use by staining or embedding for sections. Handle 

 very carefully since the killing fluid makes them rather brittle. 

 If whole mounts are desired a light stain with hematoxylin 

 is good. When mounting support the cover glass to pre- 

 vent crushing. 



Hydroids, Jelly-fish. If these are collected the jelly-fish 

 should be preserved in formalin. Obelia should be nar- 

 cotized with magnesium sulphate before killing, to get the 

 hydranths expanded. It is well to have the hydroids killed 

 in some killing fluid and preserved in alcohol, though for 

 general external study preservation in formalin is satis- 

 factory. To make whole mounts of the hydroids proceed 

 as for hydra. 



Earthworm. In the spring and early summer after a 

 soaking rain large earthworms can easily be obtained at 

 night. With a light examine the ground, preferably in a 

 garden or where there is little grass. Place the worms in 

 a can with a little soil until morning. 



To preserve put the worms in a dish or pan with enough 



