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. — An oral tentacle, magnified about 

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

 Brooks. ) Fig. 23. 



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. 



