OCELLATE HYDRO-MEDUSA. 



45 



and so on (Fig. 23), until a great number of small ter- 

 minal branches is formed. Notice the round knobs at the 

 ends of the terminal branches. 



2. Examine one of the main trunks 

 with a higher power, and notice : 



a. The double layer of large endo- 

 derm cells (Fig. 24, a) which forms the 

 solid axis of the tentacle. 



FIG. 23. 



FIG. 23. An oral tentacle, magnified about 

 eighty diameters. (Drawn from nature by W. K. 

 Brooks. ) 



b. The supporting layer. 



c. The muscular layer (Fig. 24, b). 



d. The ectoderm, with a few scattered nematocysts. 



FIG. 24. 



FIG. 24. The tips of two branches of an oral tentacle, magnified 

 two hundred and fifty diameters, from a picric acid specimen. (Drawn 

 from nature by W. K. Brooks. ) 



a. The endoderm cells, b. The muscular layer, c. Battery of nema- 

 tocysts. 



