66 



CCELENTERATES 



Hydras also reproduce asexually by budding. The buds 

 soon separate from the parent and begin an independent 

 life. Like the developing sponge, the developing hydra 

 grows until it finally becomes a fully formed hydra. 



LABORATORY STUDY 



The living brown or green hydras can usually be found in the spring or 

 fall in most fresh water ponds. They are easily collected by gathering 

 the floating leaves and overhanging grass that is immersed in the water. 

 Place this collection in a glass jar in the laboratory. In a couple of days 

 the hydras will have moved from the grass to the sides of the jar. They 

 can be examined by a small magnifying glass in the jar or be transferred 

 to a watch glass and observed under the low power of the microscope. 

 Watch the hydra contract, when jarred or touched. Note that the tentacles 

 become very short. Try feeding with a small bit of raw meat. Make 

 out the transparent ectoderm and the darker endoderm. Are there any 

 buds ? What happens to the buds when the parents contract ? 



52. Hydroids. — Hydroids are marine, hydra-like animals 

 which are united in groups forming a tree-like colony 

 (Figures 64-66). They are often mistaken for plants. 



Figure 64. — Microphotograph 



OF THE HYDROID ObELIA. 



Figure 65. — Diagram of the 

 Hydroid Bougainvillea. 



