10 A MANUAL OF ZOOLOGY 



oscula on the specimen in hand. Pull out a small piece 

 and study the structure und^r the low and the high power. 

 Make a drawing of the specimen as a whole. Make a 

 diagram to illustrate the structure as seen under the high 

 ■power. 



PHYLUM COELENTERATA 



i^ HYDROZOA 

 I. The Fresh Water Polyp or Hydra 



Examine several specimens as to size, shape, and 

 color. Decide whether the animal is free to move about 

 or not. If it moves about, what is its method? Are there 

 any specimens that seem to be double? If so, are there 

 any suggestions as to how this might occur? Are, all 

 specimens the same color? Find the following parts of the 

 body: The foot (attached portion); the body proper; the 

 body cavity (enteron) ; the mouth, and the tenta6les. What 

 is the relation of the mouth and 'the tentacles? Study 

 several specimens f or^ the number and the variability of th« 

 tentacles. Make a drawing on a large scale showing all 

 the parts studied thus far. Watch the Hydra in a jar for 

 some time turning the jar so as to vary the light. Decide 

 as to the method of locomotion and the changes in shUpe, 

 and length of both body and tentacles. If the hydra are 

 not inclined to move about they may be induced to do so 

 by suspending a small piece of meat in the water by means 

 of a thread quite near the animal. ■ To observe the method 

 of eating, place several good specimens in a watch glass 

 and with them .a ,few small bits of meat. Describe care- 

 fully what is observed. Is thi^re any evidence that other 

 things have been eaten? If so, what? Describe the action 

 of the hydr^ when irritated. Test the effect of light upon 

 the hydra by covering one side of a jar containing several 

 specimens. Are" there any evidences of co-ordination in 

 the movements of the hydra? Study live specimens and 

 stained sections under the high power. Determine the 

 extent of the stomach cavity or enteron. Is there any 

 opening (anus) for waste matter to leave the body? The 

 body wall will differentiate into three layers, two of which 

 are cellular; the outer (ectoderm), the inner (entoderm); 

 the middle or supporting layer (mesogloea) is not cellular. 



