12 Invertebrate Zoology. 



THE HYDRIFORM STAGE OF A CAMPA- 

 NULARIAN HYDROID 



(Campanularia sp^). 



External Anatomy. Examine with a low power and 

 note the more or less branching hydrocaulus or stem. It is 

 supported upon a root-like expansion or hydrorhiza. What 

 is the order of the branching? Note any structures that 

 may give flexibility to the horny, tube -like covering or peri- 

 sarc. Do you find the perisarc enlarging at its free extremi- 

 ties into bell-shaped cups or hydrotheca? The hydrothecae 

 give protection to the zooids or hydranths. Observe that 

 certain of the hydrothecae may become considerably en- 

 larged, forming gonangia. Each ripe gonangium may con- 

 tain a number of medusa buds. 



Make an enlarged drawing, naming the several parts. 



Examine a single expanded hydranth under a higher 

 power and note the position of the terminal mouth. The 

 mouth is supported upon a proboscis or manubrium. Around 

 the base of the manubrium are arranged the tentacles which, 

 during life, are capable of considerable movement Below 

 the circle of tentacles, and quite enclosed by the hydrothecae, 

 the body of the hydranth is to be noted. What is the 

 arrangement of the tentacles in a contracted zooid or 

 hydranth ? 



Use a still higher power. Do you find certain wart-like 



