CAHPANULAEIAN HTDEOID 91 



The free - swimming medusoid forms are obtained 

 by skimming the surface of the water on warm, still 

 nights with a net of bolting-cloth (for full directions 

 see Brooks's " Invertebrate Zoology "). The specimens 

 thus caught may be killed in good condition by a short 

 immersion in one-tenth per cent, osmic acid. Then 

 transfer to a watch-glass of thirty per cent, alcohol, 

 and finish the hardening in stronger grades made by 

 adding to that in the watch-glass a few drops of ninety- 

 five per cent, alcohol every few minutes. 



Method of Examination. — Living specimens free 

 from foreign bodies, algae, mud, etc., may be examined 

 in a watch-glass of sea-water. Study alcoholic material 

 in a watch-glass of fifty per cent, alcohol. Specimens 

 mounted in Canada balsam are, of course, "permanent 

 mounts," and are ready for microscopic study at any 

 time. 



MOEPHOLOGT 



Examine a cluster of the animals in a watch-glass 

 filled with fifty per cent, alcohol and note the plant- 

 like aspect of the cluster. Note also the root-like at- 

 tached end or hydrorhiza, the main stalk or hydro- 

 caulus with its branches, and the position of the zobids 

 or hydranths on the branches. Then examine both 

 living and prepared specimens, first with a low, then 

 with a high power. 



a. General Form and Structure. — "What is the general 

 shape ? How do you distinguish the base of the 

 specimen? Is the cluster a colony of animals or 

 a single animal? How are the branches ar- 

 ranged on the main stem? Are there any dif- 



