Example 2 



Preparation of a Wholemount of Pectinatella Stained 

 in Grenacher's Alcoholic Borax Carmine 



Though this description applies to the animal named, it may be used 

 equally well for any other fresh-water bryozoan or, as a matter of fact, for any 

 small invertebrate of about the same size and consistency. Pectinatella has been 

 picked only for the reason that it has the habit of turning up on the walls of 

 the aquaria in the author's laboratory. Profitable hunting grounds, if they have 

 to be sought, are the undersides of the leaves of large water plants and the 

 surfaces of branches of trees which have fallen into the water but have not 

 yet had time to decay. An old trick of European collectors was to lower a 

 length of rope into a pond in which Bryozoa were known to occur and to 

 leave it there for the summer. It was astonishing how frequently, when these 

 ropes were pulled up again in the fall, they were found to be covered with 

 colonies of Bryozoa. 



However the Bryozoa are obtained, it is necessary first that they be nar- 

 cotized. The material on which they are living is cut up and placed on the 

 bottom of a finger bowl of aquarium or pond water. Distilled water and tap 

 water are lethal to these forms. There should not be so many specimens that 

 they touch each other on the bottom of the finger bowl, and the finger bowl 

 itself should be completely filled with water. The fresh-water Bryozoa are a 

 little sensitive to heat and may not respond well to the high temperatures 

 found in some laboratories. In this case it is well to put the finger bowl con- 

 taining the specimens in an icebox or electric refrigerator, preferably one held at 

 about 10° C, and to leave them there overnight. Then they may be brought out 

 and narcotized before they have time to suffer from the increasing temperature. 



The author prefers to use menthol, which is both cheap and easy to obtain. 

 The menthol is sprinkled on the top of the water in the specimen jar. For an 

 ordinary finger bowl, about a gram of menthol will be sufficient. There is no 

 means of foretelling how long it will take the specimens to become narcotized; 

 therefore, they should be observed at intervals until they no longer are seen 

 to be contracting. However this may not be due to narcotization, so that 

 some very delicate instrument— a hair mounted in a wooden handle is excel- 

 lent—should be used to test narcotization by pushing the individual- polyps. 

 If, on receiving a push, they contract sharply, it is evident that no narcotiza- 

 tion at all has taken place, and the amount of menthol which has been 

 sprinkled on the surface should be increased greatly. If, on being pushed with 



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