COLLECTING AND PRESERVING DELICATE 

 ORGANISMS. 



BY CHARLES F. ROUSSELET, F. R. M. S. 



(Mr. Charles F. Roiisselet, of London, Knghmd, at the recent meet- 

 ing of the International Zoological Congress in Philadelphia, met Mr, 

 Ell ward Potts, of Media, Pa., by appointment, and procured from him 

 specimens of local Polyzoa of species not native in England. Among 

 these were Pectinatella, Pottsiella and Urnatella. He was desirous of 

 making the attempt to acclimatize these forms in certain canal waters in 

 London, and afterwards wrote Mr. Potts, under date of October loth, 

 1907, requesting statoblasts for this purpose; adding that "specimens 

 of these did not exist in England." Accompanying the letter Mr. Rousse- 

 let sends the detailed instructions for collecting and preserving Polyzoa 

 and Rotifera, as given below. These directions are so precise that they 

 cannot fail to be of value to students and collectors of these organisms.) 



FRESH WATER POLYZOA. 



The preparation of Polyzoa fully extended presents no 

 great difficulties, but a little practice and patience are undoubt- 

 edly required. 



As with Rotifera, these animals require to be narcotized, 

 and cocaine or eucaine i per cent, solutions have proved best 

 for this purpose. 



Polyzoa are often found in large masses, but no useful 

 purpose is served in preserving a very large colony. It is 

 much better to pick out several small characteristic and clean 

 pieces and after washing these well in water, and removing all 

 branches and weeds that may interfere, place the selected 

 pieces in a fairly large bottle of very clean water and allow 

 the animals to expand. When they are fully expanded trans- 

 fer each piece into a separate tube bottle (4 to 10 c. c), and 

 when the animals have again recovered add one drop of the 

 cocaine or eucaine soltttion and gently mix with a pipette. 

 So little of the narcotic tnust in the first instance be put in, 

 that the animals do not mind it ; they will all retract at first, 

 but soon come out again. After ten minutes add again one 



