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On a Method of Preserving Rotatoria. 

 By Charles Rousselet, F.R.M.S. 



(:Read January 20th, 1893 J 



The inability of preserving the various and beautiful forms 

 of pond life in anything like the appearance they present in life, 

 owing to the thinness of their tissues and the enormous con- 

 traction they undergo when put up in preservative fluids, has 

 always been felt with much regret by most observers. It often 

 happens also that a form is found in great numbers on one 

 occasion and then not again for many years afterwards, and 

 the utility, therefore, of being able to preserve some type 

 specimen for future reference, and for the elucidation or veri- 

 fication of anatomical details, cannot be overrated. 



During last season I made a large number of experiments in 

 order to try and solve this problem with regard to Rotifers. 

 My efforts in this direction have been suflnciently successful to 

 induce me to place before you the methods I have employed, in 

 order to allow others to experimenting the same direction. 



The Rotifers I have prepared are fully extended, very nearly 

 as transparent as in life, with their cilia, muscles, nerve threads 

 — and even the minutest anatomical details — such as the 

 vibratile tags and the very fine flagella attached to these tags 

 in Asplanchna — f nlly preserved, and often rendered more easily 

 visible. 



After carefully considering the various methods in use for 

 preserving animal tissues, which are so clearly set forth in Mr. 

 A. B. Lee's " Microtomists' Yade-Mecum," I decided to follow 

 an exclusively watery process, that is, one that would prevent 

 the dehydration of the specimen, which appears to be the chief 

 cause of the shrinkage. Alcohol, therefore, and all fluids 

 absorbing, or much denser than, water have been avoided. 



The whole process consists of four stages, namel}^ narcotizing, 

 killing, fixing and preserving, which I will describe separately. 



Narcotizing. — In dealing with Rotifers the greatest difficulty 



JouRN. Q. M. C., Series II., No 32. 14 



