Preparation of Inverlebrates for Whole Mounts and Sections 373 



COELENTERATES. 



Hydra. Place in a small amount ot water (few drops) in a shallo\v 

 dish. When animals are extended, rapidly pipette warm mercuric 

 chloride-acetic (saturated aqueous mercuric chloride, 95.0 ml.; glacial 

 acetic acid, 5.0 ml.) at them. Work the fixative from base toward oral 

 region, thereby preventing tentacles from contracting or curling. 



Sea anemones. Anesthetize overnight Avith menthol; or thirty per 

 cent magnesium chloride (50 to 100 ml.) can be added gradually over 

 a period of one hour: leave in the solution until there is no more con- 

 traction of tentacles. Siphon off the solution until anemones are just 

 barely covered. Add fixative (Susa, Bouin's, mercuric-chloride combina- 

 tions, 10% formalin sea water) slowly down the side of the container. 

 Also pipette some directly into the throats of the anemones. When 

 partially hardened, transfer into fresh tnidiluted fixative. 



Jellyfish. In sea water, while stirring, add fixative (10% formalin) 

 down side of container tmtil proportions are approxiinately 10 ml. or 

 more to 100.0 ml. of sea water. Stir for 3 or 4 minutes. After 2-3 hours, 

 change to fresh formalin. 



Medusae. Must be anesthetized; cocaine is best. Allow them to ex- 

 pand in a small dish of water, add 3-4 ml. of 1%, cocaine per 100.0 ml. 

 of water. When they do not contract, add fixative (10%, formalin) Avith 

 stirrino-. 



Corals with extended polyps. Narcotize with magnesimn sulfate and 

 fix in hot sattirated merctiric chloride plus 5% acetic acid. 

 Freezing sometimes can be tried on coelenterates. 



PLATYHELMINTHES. 



Planaria. Starve for a few days before killing. Place in a small amount 

 of water on a glass plate. When extended, add a drop of 2% aqiieotis 

 nitric acid directly on it. Follow by pipetting fixative (Gilson or 

 saturated mercuric chloride in saline) on it and then transfer into a 

 dish of fixative. 



Trematodes. Anesthetize large trematodes with menthol: | hour. 

 Then flatten by the following method: saturate filter paper with Gil- 

 son's and lay on a plate of glass. Lay worms on paper and quickly cover 

 with another sheet of saturated paper and a second plate of glass. Add 

 a weight, but not such a heavy one that the worms are crushed: 8-12 

 hoins. Remo\'e glass and paper and transfer worms to fresh fixative. A 

 single specimen can be flattened between slides, tied together and 

 dropped into fixative. After 2-3 hours, remove the string, but do not 



