Branch Coelenterata 27 



IV. — Mount one of these tentacles on a glass slide, and 

 observe its structure with the low power. How are 

 the nettle cells arranged along the tentacles } Is there 

 any difference in their arrangement near the basal end 

 of the tentacle and near its distal end ? Make a care- 

 ful drawing of a section from the basal part and of 

 one from the distal part, including in the latter the end 

 of the tentacle. 



V. — Now examine the tentacles with the high power. 



Notice the structure of the nettle cells. Make a draw- 

 ing showing a bit of the edge of the tentacle with these 

 cells imbedded in it. 



VI. — See the wart-like projections along the sides of the 

 radial canals : these are the sexual reproductive organs. 

 In some specimens these produce spermatozoa ; in others 

 they produce eggs. The sexes are therefore distinct. 



■ The eggs are fertilized by the spermatozoa which have 

 come from other medusae. Then each develops into a 

 Campanularian Hydroid. 



VII. — Make a careful diagrammatic sketch of a side view 

 of the Medusa, labelling the parts distinctly. 



THE TUBULARIAN HYDROID 



HYDRIFORM STAGE 



■ This is an animal living in salt water in rather good- 

 sized colonics. It resembles in many respects the Cam- 

 panularian Hydroid. 



I. — Examine the specimen in your watch glass through 

 a hand lens. Is the branching different from that of 

 the Campanularian Hydroid.? Does the colony seem 

 larger ? 



