28 Laboratory Guide in Zoology 



II. — Mount a small part of the specimen on a glass slide, 

 and observe it through the low power. Notice that 

 like the Campanularian Hydroid it is composed of two 

 general parts, viz. : — 



a. A firm outer covering, the perisarc. 



b. An inner protoplasmic part — the living substance. 



III. — Spread the colony out upon a flat surface and make 

 a sketch of the whole of it. Identify the following 

 divisions of the colony, and label them in your drawing : 



a. The root-like expansion — hydrorhiza — by which 

 the colony is attached to the permanent support. 



b. The upright branching stem, the hydrocaulus. 



c. The terminations of the branches of the hydrocaulus, 



without the bell-like expansion of the perisarc which 

 is present in the Campanularian Hydroid. 



d. The projecting zooids or hydranths on the ends of 

 the terminal branches. 



IV. — Examine with the low power an individual zooid. 

 Make a good-sized drawing in which you show clearly 

 the following parts, labelling them carefully: — 



a. The basal connection with the perisarc. 



b. The ring of long tentacles near the base of the 

 zooid. 



c. The ring of short tentacles toward the distal end. 



d. The projecting " proboscis " or manubrium on the 

 distal side of the short tentacles. 



e. The mouth upon the tip of the manubrium. 



V. — Study several other hydranths to see what variations 



exist. Are there always the same number of long 

 tentacles .-' of short ones ? 



VI. — Study the tentacles under a higher power. Are there 

 nettle cells present ? 



VII. — Compare this hydranth with the hydranth of the 



